From 745e3bd49f7d496779b5e67ac7a6c478c64a2a0f Mon Sep 17 00:00:00 2001
From: Mike Blumenkrantz <zmike@osg.samsung.com>
Date: Wed, 6 May 2015 12:27:58 -0400
Subject: [PATCH] update embedding interfaces again to use filling_drop feature

...and remove trailing whitespaces
---
 ports/cef/interfaces/cef_app.rs               |  39 +-
 ports/cef/interfaces/cef_auth_callback.rs     |  30 +-
 ports/cef/interfaces/cef_browser.rs           | 294 ++++++++-----
 .../interfaces/cef_browser_process_handler.rs |  36 +-
 ports/cef/interfaces/cef_callback.rs          |  56 ++-
 ports/cef/interfaces/cef_client.rs            |  69 ++--
 ports/cef/interfaces/cef_command_line.rs      |  84 ++--
 .../interfaces/cef_context_menu_handler.rs    | 110 +++--
 ports/cef/interfaces/cef_cookie.rs            | 123 +++---
 ports/cef/interfaces/cef_dialog_handler.rs    |  56 ++-
 ports/cef/interfaces/cef_display_handler.rs   |  42 +-
 ports/cef/interfaces/cef_dom.rs               | 190 ++++++---
 ports/cef/interfaces/cef_download_handler.rs  |  88 ++--
 ports/cef/interfaces/cef_download_item.rs     |  75 ++--
 ports/cef/interfaces/cef_drag_data.rs         |  90 ++--
 ports/cef/interfaces/cef_drag_handler.rs      |  27 +-
 ports/cef/interfaces/cef_find_handler.rs      |  27 +-
 ports/cef/interfaces/cef_focus_handler.rs     |  33 +-
 ports/cef/interfaces/cef_frame.rs             |  96 +++--
 ports/cef/interfaces/cef_geolocation.rs       |  27 +-
 .../cef/interfaces/cef_geolocation_handler.rs |  56 ++-
 ports/cef/interfaces/cef_jsdialog_handler.rs  |  62 +--
 ports/cef/interfaces/cef_keyboard_handler.rs  |  30 +-
 ports/cef/interfaces/cef_life_span_handler.rs |  39 +-
 ports/cef/interfaces/cef_load_handler.rs      |  36 +-
 ports/cef/interfaces/cef_menu_model.rs        | 171 +++++---
 ports/cef/interfaces/cef_navigation_entry.rs  |  54 ++-
 ports/cef/interfaces/cef_origin_whitelist.rs  |   1 +
 ports/cef/interfaces/cef_parser.rs            |   1 +
 ports/cef/interfaces/cef_path_util.rs         |   1 +
 ports/cef/interfaces/cef_print_handler.rs     |  91 ++--
 ports/cef/interfaces/cef_print_settings.rs    |  93 +++--
 ports/cef/interfaces/cef_process_message.rs   |  39 +-
 ports/cef/interfaces/cef_process_util.rs      |   1 +
 ports/cef/interfaces/cef_render_handler.rs    |  63 ++-
 .../interfaces/cef_render_process_handler.rs  |  57 ++-
 ports/cef/interfaces/cef_request.rs           | 163 +++++---
 ports/cef/interfaces/cef_request_context.rs   |  48 ++-
 .../interfaces/cef_request_context_handler.rs |  27 +-
 ports/cef/interfaces/cef_request_handler.rs   |  95 +++--
 .../interfaces/cef_resource_bundle_handler.rs |  30 +-
 ports/cef/interfaces/cef_resource_handler.rs  |  42 +-
 ports/cef/interfaces/cef_response.rs          |  54 ++-
 ports/cef/interfaces/cef_scheme.rs            |  53 ++-
 ports/cef/interfaces/cef_ssl_info.rs          |  95 +++--
 ports/cef/interfaces/cef_stream.rs            | 153 ++++---
 ports/cef/interfaces/cef_string_visitor.rs    |  27 +-
 ports/cef/interfaces/cef_task.rs              |  65 +--
 ports/cef/interfaces/cef_trace.rs             |  27 +-
 ports/cef/interfaces/cef_urlrequest.rs        |  80 ++--
 ports/cef/interfaces/cef_v8.rs                | 387 +++++++++++-------
 ports/cef/interfaces/cef_values.rs            | 351 ++++++++++------
 ports/cef/interfaces/cef_web_plugin.rs        |  88 ++--
 ports/cef/interfaces/cef_xml_reader.rs        | 111 +++--
 ports/cef/interfaces/cef_zip_reader.rs        |  60 ++-
 ports/cef/lib.rs                              |   2 +-
 ports/cef/macros.rs                           |   2 +-
 57 files changed, 2797 insertions(+), 1550 deletions(-)

diff --git a/ports/cef/interfaces/cef_app.rs b/ports/cef/interfaces/cef_app.rs
index 287cf5097b4..bdd74b11ae8 100644
--- a/ports/cef/interfaces/cef_app.rs
+++ b/ports/cef/interfaces/cef_app.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -106,13 +107,13 @@ pub struct _cef_app_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_app_t = _cef_app_t;
 
@@ -128,7 +129,8 @@ pub struct CefApp {
 impl Clone for CefApp {
   fn clone(&self) -> CefApp{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefApp {
@@ -141,7 +143,8 @@ impl Clone for CefApp {
 impl Drop for CefApp {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -156,7 +159,8 @@ impl CefApp {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_app_t) -> CefApp {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefApp {
@@ -170,7 +174,8 @@ impl CefApp {
 
   pub fn c_object_addrefed(&self) -> *mut cef_app_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -178,10 +183,10 @@ impl CefApp {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -197,7 +202,8 @@ impl CefApp {
   //
   pub fn on_before_command_line_processing(&self, process_type: &[u16],
       command_line: interfaces::CefCommandLine) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -217,7 +223,8 @@ impl CefApp {
   //
   pub fn on_register_custom_schemes(&self,
       registrar: interfaces::CefSchemeRegistrar) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -236,7 +243,8 @@ impl CefApp {
   //
   pub fn get_resource_bundle_handler(
       &self) -> interfaces::CefResourceBundleHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -252,7 +260,8 @@ impl CefApp {
   //
   pub fn get_browser_process_handler(
       &self) -> interfaces::CefBrowserProcessHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -268,7 +277,8 @@ impl CefApp {
   //
   pub fn get_render_process_handler(
       &self) -> interfaces::CefRenderProcessHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -295,7 +305,8 @@ impl CefWrap<*mut cef_app_t> for Option<CefApp> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_app_t) -> Option<CefApp> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefApp::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_auth_callback.rs b/ports/cef/interfaces/cef_auth_callback.rs
index 94681070a64..f93fb47956f 100644
--- a/ports/cef/interfaces/cef_auth_callback.rs
+++ b/ports/cef/interfaces/cef_auth_callback.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -71,13 +72,13 @@ pub struct _cef_auth_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_auth_callback_t = _cef_auth_callback_t;
 
@@ -93,7 +94,8 @@ pub struct CefAuthCallback {
 impl Clone for CefAuthCallback {
   fn clone(&self) -> CefAuthCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefAuthCallback {
@@ -106,7 +108,8 @@ impl Clone for CefAuthCallback {
 impl Drop for CefAuthCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -121,7 +124,8 @@ impl CefAuthCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_auth_callback_t) -> CefAuthCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefAuthCallback {
@@ -135,7 +139,8 @@ impl CefAuthCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_auth_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -143,17 +148,18 @@ impl CefAuthCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Continue the authentication request.
   //
   pub fn cont(&self, username: &[u16], password: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -169,7 +175,8 @@ impl CefAuthCallback {
   // Cancel the authentication request.
   //
   pub fn cancel(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -196,7 +203,8 @@ impl CefWrap<*mut cef_auth_callback_t> for Option<CefAuthCallback> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_auth_callback_t) -> Option<CefAuthCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefAuthCallback::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_browser.rs b/ports/cef/interfaces/cef_browser.rs
index 30a580b6d13..46c9fcaf100 100644
--- a/ports/cef/interfaces/cef_browser.rs
+++ b/ports/cef/interfaces/cef_browser.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -186,13 +187,13 @@ pub struct _cef_browser_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_browser_t = _cef_browser_t;
 
@@ -210,7 +211,8 @@ pub struct CefBrowser {
 impl Clone for CefBrowser {
   fn clone(&self) -> CefBrowser{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefBrowser {
@@ -223,7 +225,8 @@ impl Clone for CefBrowser {
 impl Drop for CefBrowser {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -238,7 +241,8 @@ impl CefBrowser {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_browser_t) -> CefBrowser {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefBrowser {
@@ -252,7 +256,8 @@ impl CefBrowser {
 
   pub fn c_object_addrefed(&self) -> *mut cef_browser_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -260,10 +265,10 @@ impl CefBrowser {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -271,7 +276,8 @@ impl CefBrowser {
   // browser process.
   //
   pub fn get_host(&self) -> interfaces::CefBrowserHost {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -285,7 +291,8 @@ impl CefBrowser {
   // Returns true (1) if the browser can navigate backwards.
   //
   pub fn can_go_back(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -299,7 +306,8 @@ impl CefBrowser {
   // Navigate backwards.
   //
   pub fn go_back(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -313,7 +321,8 @@ impl CefBrowser {
   // Returns true (1) if the browser can navigate forwards.
   //
   pub fn can_go_forward(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -327,7 +336,8 @@ impl CefBrowser {
   // Navigate forwards.
   //
   pub fn go_forward(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -341,7 +351,8 @@ impl CefBrowser {
   // Returns true (1) if the browser is currently loading.
   //
   pub fn is_loading(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -355,7 +366,8 @@ impl CefBrowser {
   // Reload the current page.
   //
   pub fn reload(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -369,7 +381,8 @@ impl CefBrowser {
   // Reload the current page ignoring any cached data.
   //
   pub fn reload_ignore_cache(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -383,7 +396,8 @@ impl CefBrowser {
   // Stop loading the page.
   //
   pub fn stop_load(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -397,7 +411,8 @@ impl CefBrowser {
   // Returns the globally unique identifier for this browser.
   //
   pub fn get_identifier(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -412,7 +427,8 @@ impl CefBrowser {
   // object.
   //
   pub fn is_same(&self, that: interfaces::CefBrowser) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -427,7 +443,8 @@ impl CefBrowser {
   // Returns true (1) if the window is a popup window.
   //
   pub fn is_popup(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -441,7 +458,8 @@ impl CefBrowser {
   // Returns true (1) if a document has been loaded in the browser.
   //
   pub fn has_document(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -455,7 +473,8 @@ impl CefBrowser {
   // Returns the main (top-level) frame for the browser window.
   //
   pub fn get_main_frame(&self) -> interfaces::CefFrame {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -469,7 +488,8 @@ impl CefBrowser {
   // Returns the focused frame for the browser window.
   //
   pub fn get_focused_frame(&self) -> interfaces::CefFrame {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -483,7 +503,8 @@ impl CefBrowser {
   // Returns the frame with the specified identifier, or NULL if not found.
   //
   pub fn get_frame_byident(&self, identifier: i64) -> interfaces::CefFrame {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -498,7 +519,8 @@ impl CefBrowser {
   // Returns the frame with the specified name, or NULL if not found.
   //
   pub fn get_frame(&self, name: &[u16]) -> interfaces::CefFrame {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -513,7 +535,8 @@ impl CefBrowser {
   // Returns the number of frames that currently exist.
   //
   pub fn get_frame_count(&self) -> libc::size_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -528,7 +551,8 @@ impl CefBrowser {
   //
   pub fn get_frame_identifiers(&self, identifiers_count: *mut libc::size_t,
       identifiers: *mut i64) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -544,7 +568,8 @@ impl CefBrowser {
   // Returns the names of all existing frames.
   //
   pub fn get_frame_names(&self, names: Vec<String>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -561,7 +586,8 @@ impl CefBrowser {
   //
   pub fn send_process_message(&self, target_process: interfaces::CefProcessId,
       message: interfaces::CefProcessMessage) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -590,7 +616,8 @@ impl CefWrap<*mut cef_browser_t> for Option<CefBrowser> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_browser_t) -> Option<CefBrowser> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefBrowser::from_c_object_addref(c_object))
@@ -625,13 +652,13 @@ pub struct _cef_run_file_dialog_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_run_file_dialog_callback_t = _cef_run_file_dialog_callback_t;
 
@@ -647,7 +674,8 @@ pub struct CefRunFileDialogCallback {
 impl Clone for CefRunFileDialogCallback {
   fn clone(&self) -> CefRunFileDialogCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefRunFileDialogCallback {
@@ -660,7 +688,8 @@ impl Clone for CefRunFileDialogCallback {
 impl Drop for CefRunFileDialogCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -675,7 +704,8 @@ impl CefRunFileDialogCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_run_file_dialog_callback_t) -> CefRunFileDialogCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefRunFileDialogCallback {
@@ -689,7 +719,8 @@ impl CefRunFileDialogCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_run_file_dialog_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -697,10 +728,10 @@ impl CefRunFileDialogCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -712,7 +743,8 @@ impl CefRunFileDialogCallback {
   //
   pub fn on_file_dialog_dismissed(&self, selected_accept_filter: libc::c_int,
       file_paths: Vec<String>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -741,7 +773,8 @@ impl CefWrap<*mut cef_run_file_dialog_callback_t> for Option<CefRunFileDialogCal
     }
   }
   unsafe fn to_rust(c_object: *mut cef_run_file_dialog_callback_t) -> Option<CefRunFileDialogCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefRunFileDialogCallback::from_c_object_addref(c_object))
@@ -775,13 +808,13 @@ pub struct _cef_navigation_entry_visitor_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_navigation_entry_visitor_t = _cef_navigation_entry_visitor_t;
 
@@ -797,7 +830,8 @@ pub struct CefNavigationEntryVisitor {
 impl Clone for CefNavigationEntryVisitor {
   fn clone(&self) -> CefNavigationEntryVisitor{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefNavigationEntryVisitor {
@@ -810,7 +844,8 @@ impl Clone for CefNavigationEntryVisitor {
 impl Drop for CefNavigationEntryVisitor {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -825,7 +860,8 @@ impl CefNavigationEntryVisitor {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_navigation_entry_visitor_t) -> CefNavigationEntryVisitor {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefNavigationEntryVisitor {
@@ -839,7 +875,8 @@ impl CefNavigationEntryVisitor {
 
   pub fn c_object_addrefed(&self) -> *mut cef_navigation_entry_visitor_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -847,10 +884,10 @@ impl CefNavigationEntryVisitor {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -863,7 +900,8 @@ impl CefNavigationEntryVisitor {
   pub fn visit(&self, entry: interfaces::CefNavigationEntry,
       current: libc::c_int, index: libc::c_int,
       total: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -894,7 +932,8 @@ impl CefWrap<*mut cef_navigation_entry_visitor_t> for Option<CefNavigationEntryV
     }
   }
   unsafe fn to_rust(c_object: *mut cef_navigation_entry_visitor_t) -> Option<CefNavigationEntryVisitor> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefNavigationEntryVisitor::from_c_object_addref(c_object))
@@ -1292,13 +1331,13 @@ pub struct _cef_browser_host_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_browser_host_t = _cef_browser_host_t;
 
@@ -1316,7 +1355,8 @@ pub struct CefBrowserHost {
 impl Clone for CefBrowserHost {
   fn clone(&self) -> CefBrowserHost{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefBrowserHost {
@@ -1329,7 +1369,8 @@ impl Clone for CefBrowserHost {
 impl Drop for CefBrowserHost {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -1344,7 +1385,8 @@ impl CefBrowserHost {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_browser_host_t) -> CefBrowserHost {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefBrowserHost {
@@ -1358,7 +1400,8 @@ impl CefBrowserHost {
 
   pub fn c_object_addrefed(&self) -> *mut cef_browser_host_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -1366,17 +1409,18 @@ impl CefBrowserHost {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Returns the hosted browser object.
   //
   pub fn get_browser(&self) -> interfaces::CefBrowser {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1397,7 +1441,8 @@ impl CefBrowserHost {
   // information.
   //
   pub fn close_browser(&self, force_close: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1412,7 +1457,8 @@ impl CefBrowserHost {
   // Set whether the browser is focused.
   //
   pub fn set_focus(&self, focus: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1428,7 +1474,8 @@ impl CefBrowserHost {
   // (minimized/unminimized, app hidden/unhidden, etc). Only used on Mac OS X.
   //
   pub fn set_window_visibility(&self, visible: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1443,7 +1490,8 @@ impl CefBrowserHost {
   // Retrieve the window handle for this browser.
   //
   pub fn get_window_handle(&self) -> types::cef_window_handle_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1459,7 +1507,8 @@ impl CefBrowserHost {
   // with custom handling of modal windows.
   //
   pub fn get_opener_window_handle(&self) -> types::cef_window_handle_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1473,7 +1522,8 @@ impl CefBrowserHost {
   // Returns the client for this browser.
   //
   pub fn get_client(&self) -> interfaces::CefClient {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1487,7 +1537,8 @@ impl CefBrowserHost {
   // Returns the request context for this browser.
   //
   pub fn get_request_context(&self) -> interfaces::CefRequestContext {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1502,7 +1553,8 @@ impl CefBrowserHost {
   // can only be called on the UI thread.
   //
   pub fn get_zoom_level(&self) -> libc::c_double {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1518,7 +1570,8 @@ impl CefBrowserHost {
   // Otherwise, the change will be applied asynchronously on the UI thread.
   //
   pub fn set_zoom_level(&self, zoomLevel: libc::c_double) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1549,7 +1602,8 @@ impl CefBrowserHost {
       title: &[u16], default_file_path: &[u16], accept_filters: Vec<String>,
       selected_accept_filter: libc::c_int,
       callback: interfaces::CefRunFileDialogCallback) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1569,7 +1623,8 @@ impl CefBrowserHost {
   // Download the file at |url| using cef_download_handler_t.
   //
   pub fn start_download(&self, url: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1584,7 +1639,8 @@ impl CefBrowserHost {
   // Print the current browser contents.
   //
   pub fn print(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1605,7 +1661,8 @@ impl CefBrowserHost {
   pub fn find(&self, identifier: libc::c_int, searchText: &[u16],
       forward: libc::c_int, matchCase: libc::c_int, findNext: libc::c_int) -> (
       ) {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1624,7 +1681,8 @@ impl CefBrowserHost {
   // Cancel all searches that are currently going on.
   //
   pub fn stop_finding(&self, clearSelection: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1642,7 +1700,8 @@ impl CefBrowserHost {
   pub fn show_dev_tools(&self, windowInfo: &interfaces::CefWindowInfo,
       client: interfaces::CefClient, settings: &interfaces::CefBrowserSettings,
       inspect_element_at: &types::cef_point_t) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1661,7 +1720,8 @@ impl CefBrowserHost {
   // instance.
   //
   pub fn close_dev_tools(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1681,7 +1741,8 @@ impl CefBrowserHost {
   pub fn get_navigation_entries(&self,
       visitor: interfaces::CefNavigationEntryVisitor,
       current_only: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1697,7 +1758,8 @@ impl CefBrowserHost {
   // Set whether mouse cursor change is disabled.
   //
   pub fn set_mouse_cursor_change_disabled(&self, disabled: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1712,7 +1774,8 @@ impl CefBrowserHost {
   // Returns true (1) if mouse cursor change is disabled.
   //
   pub fn is_mouse_cursor_change_disabled(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1727,7 +1790,8 @@ impl CefBrowserHost {
   // function will replace it with the specified |word|.
   //
   pub fn replace_misspelling(&self, word: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1742,7 +1806,8 @@ impl CefBrowserHost {
   // Add the specified |word| to the spelling dictionary.
   //
   pub fn add_word_to_dictionary(&self, word: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1757,7 +1822,8 @@ impl CefBrowserHost {
   // Returns true (1) if window rendering is disabled.
   //
   pub fn is_window_rendering_disabled(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1774,7 +1840,8 @@ impl CefBrowserHost {
   // function is only used when window rendering is disabled.
   //
   pub fn was_resized(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1790,7 +1857,8 @@ impl CefBrowserHost {
   // hidden. This function is only used when window rendering is disabled.
   //
   pub fn was_hidden(&self, hidden: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1810,7 +1878,8 @@ impl CefBrowserHost {
   // disabled.
   //
   pub fn notify_screen_info_changed(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1826,7 +1895,8 @@ impl CefBrowserHost {
   // disabled.
   //
   pub fn invalidate(&self, ty: types::cef_paint_element_type_t) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1841,7 +1911,8 @@ impl CefBrowserHost {
   // Send a key event to the browser.
   //
   pub fn send_key_event(&self, event: &interfaces::CefKeyEvent) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1859,7 +1930,8 @@ impl CefBrowserHost {
   pub fn send_mouse_click_event(&self, event: &interfaces::CefMouseEvent,
       ty: types::cef_mouse_button_type_t, mouseUp: libc::c_int,
       clickCount: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1879,7 +1951,8 @@ impl CefBrowserHost {
   //
   pub fn send_mouse_move_event(&self, event: &interfaces::CefMouseEvent,
       mouseLeave: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1900,7 +1973,8 @@ impl CefBrowserHost {
   //
   pub fn send_mouse_wheel_event(&self, event: &interfaces::CefMouseEvent,
       deltaX: libc::c_int, deltaY: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1917,7 +1991,8 @@ impl CefBrowserHost {
   // Send a focus event to the browser.
   //
   pub fn send_focus_event(&self, setFocus: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1932,7 +2007,8 @@ impl CefBrowserHost {
   // Send a capture lost event to the browser.
   //
   pub fn send_capture_lost_event(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1947,7 +2023,8 @@ impl CefBrowserHost {
   // resized. This function is only used on Windows and Linux.
   //
   pub fn notify_move_or_resize_started(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1962,7 +2039,8 @@ impl CefBrowserHost {
   // window rendering is disabled.
   //
   pub fn get_nstext_input_context(&self) -> types::cef_text_input_context_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1978,7 +2056,8 @@ impl CefBrowserHost {
   //
   pub fn handle_key_event_before_text_input_client(&self,
       keyEvent: types::cef_event_handle_t) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1994,7 +2073,8 @@ impl CefBrowserHost {
   //
   pub fn handle_key_event_after_text_input_client(&self,
       keyEvent: types::cef_event_handle_t) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2017,7 +2097,8 @@ impl CefBrowserHost {
   pub fn drag_target_drag_enter(&self, drag_data: interfaces::CefDragData,
       event: &interfaces::CefMouseEvent,
       allowed_ops: types::cef_drag_operations_mask_t) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2038,7 +2119,8 @@ impl CefBrowserHost {
   //
   pub fn drag_target_drag_over(&self, event: &interfaces::CefMouseEvent,
       allowed_ops: types::cef_drag_operations_mask_t) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2056,7 +2138,8 @@ impl CefBrowserHost {
   // rendering is disabled.
   //
   pub fn drag_target_drag_leave(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2074,7 +2157,8 @@ impl CefBrowserHost {
   // is disabled.
   //
   pub fn drag_target_drop(&self, event: &interfaces::CefMouseEvent) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2096,7 +2180,8 @@ impl CefBrowserHost {
   //
   pub fn drag_source_ended_at(&self, x: libc::c_int, y: libc::c_int,
       op: types::cef_drag_operations_mask_t) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2118,7 +2203,8 @@ impl CefBrowserHost {
   // This function is only used when window rendering is disabled.
   //
   pub fn drag_source_system_drag_ended(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2134,7 +2220,8 @@ impl CefBrowserHost {
   // this function.
   //
   pub fn initialize_compositing(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2203,7 +2290,8 @@ impl CefWrap<*mut cef_browser_host_t> for Option<CefBrowserHost> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_browser_host_t) -> Option<CefBrowserHost> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefBrowserHost::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_browser_process_handler.rs b/ports/cef/interfaces/cef_browser_process_handler.rs
index fe287c545a1..672247169fd 100644
--- a/ports/cef/interfaces/cef_browser_process_handler.rs
+++ b/ports/cef/interfaces/cef_browser_process_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -96,13 +97,13 @@ pub struct _cef_browser_process_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_browser_process_handler_t = _cef_browser_process_handler_t;
 
@@ -119,7 +120,8 @@ pub struct CefBrowserProcessHandler {
 impl Clone for CefBrowserProcessHandler {
   fn clone(&self) -> CefBrowserProcessHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefBrowserProcessHandler {
@@ -132,7 +134,8 @@ impl Clone for CefBrowserProcessHandler {
 impl Drop for CefBrowserProcessHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -147,7 +150,8 @@ impl CefBrowserProcessHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_browser_process_handler_t) -> CefBrowserProcessHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefBrowserProcessHandler {
@@ -161,7 +165,8 @@ impl CefBrowserProcessHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_browser_process_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -169,10 +174,10 @@ impl CefBrowserProcessHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -180,7 +185,8 @@ impl CefBrowserProcessHandler {
   // has been initialized.
   //
   pub fn on_context_initialized(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -199,7 +205,8 @@ impl CefBrowserProcessHandler {
   //
   pub fn on_before_child_process_launch(&self,
       command_line: interfaces::CefCommandLine) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -219,7 +226,8 @@ impl CefBrowserProcessHandler {
   //
   pub fn on_render_process_thread_created(&self,
       extra_info: interfaces::CefListValue) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -235,7 +243,8 @@ impl CefBrowserProcessHandler {
   // provided then printing will not be supported on the Linux platform.
   //
   pub fn get_print_handler(&self) -> interfaces::CefPrintHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -262,7 +271,8 @@ impl CefWrap<*mut cef_browser_process_handler_t> for Option<CefBrowserProcessHan
     }
   }
   unsafe fn to_rust(c_object: *mut cef_browser_process_handler_t) -> Option<CefBrowserProcessHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefBrowserProcessHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_callback.rs b/ports/cef/interfaces/cef_callback.rs
index fdf78a191b6..ef2452ff71d 100644
--- a/ports/cef/interfaces/cef_callback.rs
+++ b/ports/cef/interfaces/cef_callback.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -68,13 +69,13 @@ pub struct _cef_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_callback_t = _cef_callback_t;
 
@@ -89,7 +90,8 @@ pub struct CefCallback {
 impl Clone for CefCallback {
   fn clone(&self) -> CefCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefCallback {
@@ -102,7 +104,8 @@ impl Clone for CefCallback {
 impl Drop for CefCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -117,7 +120,8 @@ impl CefCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_callback_t) -> CefCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefCallback {
@@ -131,7 +135,8 @@ impl CefCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -139,17 +144,18 @@ impl CefCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Continue processing.
   //
   pub fn cont(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -163,7 +169,8 @@ impl CefCallback {
   // Cancel processing.
   //
   pub fn cancel(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -190,7 +197,8 @@ impl CefWrap<*mut cef_callback_t> for Option<CefCallback> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_callback_t) -> Option<CefCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefCallback::from_c_object_addref(c_object))
@@ -218,13 +226,13 @@ pub struct _cef_completion_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_completion_callback_t = _cef_completion_callback_t;
 
@@ -239,7 +247,8 @@ pub struct CefCompletionCallback {
 impl Clone for CefCompletionCallback {
   fn clone(&self) -> CefCompletionCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefCompletionCallback {
@@ -252,7 +261,8 @@ impl Clone for CefCompletionCallback {
 impl Drop for CefCompletionCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -267,7 +277,8 @@ impl CefCompletionCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_completion_callback_t) -> CefCompletionCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefCompletionCallback {
@@ -281,7 +292,8 @@ impl CefCompletionCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_completion_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -289,17 +301,18 @@ impl CefCompletionCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Method that will be called once the task is complete.
   //
   pub fn on_complete(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -326,7 +339,8 @@ impl CefWrap<*mut cef_completion_callback_t> for Option<CefCompletionCallback> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_completion_callback_t) -> Option<CefCompletionCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefCompletionCallback::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_client.rs b/ports/cef/interfaces/cef_client.rs
index 66f099a4d37..e49632d5f96 100644
--- a/ports/cef/interfaces/cef_client.rs
+++ b/ports/cef/interfaces/cef_client.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -157,13 +158,13 @@ pub struct _cef_client_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_client_t = _cef_client_t;
 
@@ -178,7 +179,8 @@ pub struct CefClient {
 impl Clone for CefClient {
   fn clone(&self) -> CefClient{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefClient {
@@ -191,7 +193,8 @@ impl Clone for CefClient {
 impl Drop for CefClient {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -206,7 +209,8 @@ impl CefClient {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_client_t) -> CefClient {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefClient {
@@ -220,7 +224,8 @@ impl CefClient {
 
   pub fn c_object_addrefed(&self) -> *mut cef_client_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -228,10 +233,10 @@ impl CefClient {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -239,7 +244,8 @@ impl CefClient {
   // implementation will be used.
   //
   pub fn get_context_menu_handler(&self) -> interfaces::CefContextMenuHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -254,7 +260,8 @@ impl CefClient {
   // implementation will be used.
   //
   pub fn get_dialog_handler(&self) -> interfaces::CefDialogHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -268,7 +275,8 @@ impl CefClient {
   // Return the handler for browser display state events.
   //
   pub fn get_display_handler(&self) -> interfaces::CefDisplayHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -283,7 +291,8 @@ impl CefClient {
   // will not be allowed.
   //
   pub fn get_download_handler(&self) -> interfaces::CefDownloadHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -297,7 +306,8 @@ impl CefClient {
   // Return the handler for drag events.
   //
   pub fn get_drag_handler(&self) -> interfaces::CefDragHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -311,7 +321,8 @@ impl CefClient {
   // Return the handler for find result events.
   //
   pub fn get_find_handler(&self) -> interfaces::CefFindHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -325,7 +336,8 @@ impl CefClient {
   // Return the handler for focus events.
   //
   pub fn get_focus_handler(&self) -> interfaces::CefFocusHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -340,7 +352,8 @@ impl CefClient {
   // provided geolocation access will be denied by default.
   //
   pub fn get_geolocation_handler(&self) -> interfaces::CefGeolocationHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -355,7 +368,8 @@ impl CefClient {
   // default implementation will be used.
   //
   pub fn get_jsdialog_handler(&self) -> interfaces::CefJSDialogHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -369,7 +383,8 @@ impl CefClient {
   // Return the handler for keyboard events.
   //
   pub fn get_keyboard_handler(&self) -> interfaces::CefKeyboardHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -383,7 +398,8 @@ impl CefClient {
   // Return the handler for browser life span events.
   //
   pub fn get_life_span_handler(&self) -> interfaces::CefLifeSpanHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -397,7 +413,8 @@ impl CefClient {
   // Return the handler for browser load status events.
   //
   pub fn get_load_handler(&self) -> interfaces::CefLoadHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -411,7 +428,8 @@ impl CefClient {
   // Return the handler for off-screen rendering events.
   //
   pub fn get_render_handler(&self) -> interfaces::CefRenderHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -425,7 +443,8 @@ impl CefClient {
   // Return the handler for browser request events.
   //
   pub fn get_request_handler(&self) -> interfaces::CefRequestHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -443,7 +462,8 @@ impl CefClient {
   pub fn on_process_message_received(&self, browser: interfaces::CefBrowser,
       source_process: interfaces::CefProcessId,
       message: interfaces::CefProcessMessage) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -473,7 +493,8 @@ impl CefWrap<*mut cef_client_t> for Option<CefClient> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_client_t) -> Option<CefClient> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefClient::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_command_line.rs b/ports/cef/interfaces/cef_command_line.rs
index f46d4f1044c..53674ef25ba 100644
--- a/ports/cef/interfaces/cef_command_line.rs
+++ b/ports/cef/interfaces/cef_command_line.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -200,13 +201,13 @@ pub struct _cef_command_line_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_command_line_t = _cef_command_line_t;
 
@@ -228,7 +229,8 @@ pub struct CefCommandLine {
 impl Clone for CefCommandLine {
   fn clone(&self) -> CefCommandLine{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefCommandLine {
@@ -241,7 +243,8 @@ impl Clone for CefCommandLine {
 impl Drop for CefCommandLine {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -256,7 +259,8 @@ impl CefCommandLine {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_command_line_t) -> CefCommandLine {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefCommandLine {
@@ -270,7 +274,8 @@ impl CefCommandLine {
 
   pub fn c_object_addrefed(&self) -> *mut cef_command_line_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -278,10 +283,10 @@ impl CefCommandLine {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -289,7 +294,8 @@ impl CefCommandLine {
   // if this function returns false (0).
   //
   pub fn is_valid(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -304,7 +310,8 @@ impl CefCommandLine {
   // expose read-only objects.
   //
   pub fn is_read_only(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -318,7 +325,8 @@ impl CefCommandLine {
   // Returns a writable copy of this object.
   //
   pub fn copy(&self) -> interfaces::CefCommandLine {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -334,7 +342,8 @@ impl CefCommandLine {
   // supported on non-Windows platforms.
   //
   pub fn init_from_argv(&self, argc: libc::c_int, argv: &&str) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -351,7 +360,8 @@ impl CefCommandLine {
   // GetCommandLineW(). This function is only supported on Windows.
   //
   pub fn init_from_string(&self, command_line: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -367,7 +377,8 @@ impl CefCommandLine {
   // component unchanged.
   //
   pub fn reset(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -382,7 +393,8 @@ impl CefCommandLine {
   // array: { program, [(--|-|/)switch[=value]]*, [--], [argument]* }
   //
   pub fn get_argv(&self, argv: Vec<String>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -399,7 +411,8 @@ impl CefCommandLine {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_command_line_string(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -414,7 +427,8 @@ impl CefCommandLine {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_program(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -428,7 +442,8 @@ impl CefCommandLine {
   // Set the program part of the command line string (the first item).
   //
   pub fn set_program(&self, program: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -443,7 +458,8 @@ impl CefCommandLine {
   // Returns true (1) if the command line has switches.
   //
   pub fn has_switches(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -457,7 +473,8 @@ impl CefCommandLine {
   // Returns true (1) if the command line contains the given switch.
   //
   pub fn has_switch(&self, name: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -474,7 +491,8 @@ impl CefCommandLine {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_switch_value(&self, name: &[u16]) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -490,7 +508,8 @@ impl CefCommandLine {
   // NULL string is returned.
   //
   pub fn get_switches(&self, switches: HashMap<String,String>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -506,7 +525,8 @@ impl CefCommandLine {
   // pass an NULL value string.
   //
   pub fn append_switch(&self, name: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -521,7 +541,8 @@ impl CefCommandLine {
   // Add a switch with the specified value to the end of the command line.
   //
   pub fn append_switch_with_value(&self, name: &[u16], value: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -537,7 +558,8 @@ impl CefCommandLine {
   // True if there are remaining command line arguments.
   //
   pub fn has_arguments(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -551,7 +573,8 @@ impl CefCommandLine {
   // Get the remaining command line arguments.
   //
   pub fn get_arguments(&self, arguments: Vec<String>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -566,7 +589,8 @@ impl CefCommandLine {
   // Add an argument to the end of the command line.
   //
   pub fn append_argument(&self, argument: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -582,7 +606,8 @@ impl CefCommandLine {
   // "valgrind" or "gdb --args".
   //
   pub fn prepend_wrapper(&self, wrapper: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -633,7 +658,8 @@ impl CefWrap<*mut cef_command_line_t> for Option<CefCommandLine> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_command_line_t) -> Option<CefCommandLine> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefCommandLine::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_context_menu_handler.rs b/ports/cef/interfaces/cef_context_menu_handler.rs
index 3441b775be5..dedb9fd5c64 100644
--- a/ports/cef/interfaces/cef_context_menu_handler.rs
+++ b/ports/cef/interfaces/cef_context_menu_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -99,13 +100,13 @@ pub struct _cef_context_menu_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_context_menu_handler_t = _cef_context_menu_handler_t;
 
@@ -121,7 +122,8 @@ pub struct CefContextMenuHandler {
 impl Clone for CefContextMenuHandler {
   fn clone(&self) -> CefContextMenuHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefContextMenuHandler {
@@ -134,7 +136,8 @@ impl Clone for CefContextMenuHandler {
 impl Drop for CefContextMenuHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -149,7 +152,8 @@ impl CefContextMenuHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_context_menu_handler_t) -> CefContextMenuHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefContextMenuHandler {
@@ -163,7 +167,8 @@ impl CefContextMenuHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_context_menu_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -171,10 +176,10 @@ impl CefContextMenuHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -187,7 +192,8 @@ impl CefContextMenuHandler {
   pub fn on_before_context_menu(&self, browser: interfaces::CefBrowser,
       frame: interfaces::CefFrame, params: interfaces::CefContextMenuParams,
       model: interfaces::CefMenuModel) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -214,7 +220,8 @@ impl CefContextMenuHandler {
       frame: interfaces::CefFrame, params: interfaces::CefContextMenuParams,
       command_id: libc::c_int,
       event_flags: types::cef_event_flags_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -235,7 +242,8 @@ impl CefContextMenuHandler {
   //
   pub fn on_context_menu_dismissed(&self, browser: interfaces::CefBrowser,
       frame: interfaces::CefFrame) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -264,7 +272,8 @@ impl CefWrap<*mut cef_context_menu_handler_t> for Option<CefContextMenuHandler>
     }
   }
   unsafe fn to_rust(c_object: *mut cef_context_menu_handler_t) -> Option<CefContextMenuHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefContextMenuHandler::from_c_object_addref(c_object))
@@ -419,13 +428,13 @@ pub struct _cef_context_menu_params_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_context_menu_params_t = _cef_context_menu_params_t;
 
@@ -441,7 +450,8 @@ pub struct CefContextMenuParams {
 impl Clone for CefContextMenuParams {
   fn clone(&self) -> CefContextMenuParams{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefContextMenuParams {
@@ -454,7 +464,8 @@ impl Clone for CefContextMenuParams {
 impl Drop for CefContextMenuParams {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -469,7 +480,8 @@ impl CefContextMenuParams {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_context_menu_params_t) -> CefContextMenuParams {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefContextMenuParams {
@@ -483,7 +495,8 @@ impl CefContextMenuParams {
 
   pub fn c_object_addrefed(&self) -> *mut cef_context_menu_params_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -491,10 +504,10 @@ impl CefContextMenuParams {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -502,7 +515,8 @@ impl CefContextMenuParams {
   // Coords are relative to the associated RenderView's origin.
   //
   pub fn get_xcoord(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -517,7 +531,8 @@ impl CefContextMenuParams {
   // Coords are relative to the associated RenderView's origin.
   //
   pub fn get_ycoord(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -532,7 +547,8 @@ impl CefContextMenuParams {
   // invoked on.
   //
   pub fn get_type_flags(&self) -> types::cef_context_menu_type_flags_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -548,7 +564,8 @@ impl CefContextMenuParams {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_link_url(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -564,7 +581,8 @@ impl CefContextMenuParams {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_unfiltered_link_url(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -580,7 +598,8 @@ impl CefContextMenuParams {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_source_url(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -595,7 +614,8 @@ impl CefContextMenuParams {
   // NULL contents.
   //
   pub fn has_image_contents(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -610,7 +630,8 @@ impl CefContextMenuParams {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_page_url(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -625,7 +646,8 @@ impl CefContextMenuParams {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_frame_url(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -641,7 +663,8 @@ impl CefContextMenuParams {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_frame_charset(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -655,7 +678,8 @@ impl CefContextMenuParams {
   // Returns the type of context node that the context menu was invoked on.
   //
   pub fn get_media_type(&self) -> types::cef_context_menu_media_type_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -671,7 +695,8 @@ impl CefContextMenuParams {
   //
   pub fn get_media_state_flags(
       &self) -> types::cef_context_menu_media_state_flags_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -687,7 +712,8 @@ impl CefContextMenuParams {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_selection_text(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -703,7 +729,8 @@ impl CefContextMenuParams {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_misspelled_word(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -720,7 +747,8 @@ impl CefContextMenuParams {
   //
   pub fn get_dictionary_suggestions(&self,
       suggestions: Vec<String>) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -735,7 +763,8 @@ impl CefContextMenuParams {
   // Returns true (1) if the context menu was invoked on an editable node.
   //
   pub fn is_editable(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -750,7 +779,8 @@ impl CefContextMenuParams {
   // spell-check is enabled.
   //
   pub fn is_spell_check_enabled(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -766,7 +796,8 @@ impl CefContextMenuParams {
   //
   pub fn get_edit_state_flags(
       &self) -> types::cef_context_menu_edit_state_flags_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -793,7 +824,8 @@ impl CefWrap<*mut cef_context_menu_params_t> for Option<CefContextMenuParams> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_context_menu_params_t) -> Option<CefContextMenuParams> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefContextMenuParams::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_cookie.rs b/ports/cef/interfaces/cef_cookie.rs
index 38291a8b7c9..1b1090e9499 100644
--- a/ports/cef/interfaces/cef_cookie.rs
+++ b/ports/cef/interfaces/cef_cookie.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -138,13 +139,13 @@ pub struct _cef_cookie_manager_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_cookie_manager_t = _cef_cookie_manager_t;
 
@@ -160,7 +161,8 @@ pub struct CefCookieManager {
 impl Clone for CefCookieManager {
   fn clone(&self) -> CefCookieManager{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefCookieManager {
@@ -173,7 +175,8 @@ impl Clone for CefCookieManager {
 impl Drop for CefCookieManager {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -188,7 +191,8 @@ impl CefCookieManager {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_cookie_manager_t) -> CefCookieManager {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefCookieManager {
@@ -202,7 +206,8 @@ impl CefCookieManager {
 
   pub fn c_object_addrefed(&self) -> *mut cef_cookie_manager_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -210,10 +215,10 @@ impl CefCookieManager {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -224,7 +229,8 @@ impl CefCookieManager {
   //
   pub fn set_supported_schemes(&self, schemes: Vec<String>,
       callback: interfaces::CefCompletionCallback) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -243,7 +249,8 @@ impl CefCookieManager {
   //
   pub fn visit_all_cookies(&self,
       visitor: interfaces::CefCookieVisitor) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -263,7 +270,8 @@ impl CefCookieManager {
   //
   pub fn visit_url_cookies(&self, url: &[u16], includeHttpOnly: libc::c_int,
       visitor: interfaces::CefCookieVisitor) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -287,7 +295,8 @@ impl CefCookieManager {
   //
   pub fn set_cookie(&self, url: &[u16], cookie: &interfaces::CefCookie,
       callback: interfaces::CefSetCookieCallback) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -313,7 +322,8 @@ impl CefCookieManager {
   //
   pub fn delete_cookies(&self, url: &[u16], cookie_name: &[u16],
       callback: interfaces::CefDeleteCookiesCallback) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -339,7 +349,8 @@ impl CefCookieManager {
   pub fn set_storage_path(&self, path: &[u16],
       persist_session_cookies: libc::c_int,
       callback: interfaces::CefCompletionCallback) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -359,7 +370,8 @@ impl CefCookieManager {
   //
   pub fn flush_store(&self,
       callback: interfaces::CefCompletionCallback) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -424,7 +436,8 @@ impl CefWrap<*mut cef_cookie_manager_t> for Option<CefCookieManager> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_cookie_manager_t) -> Option<CefCookieManager> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefCookieManager::from_c_object_addref(c_object))
@@ -458,13 +471,13 @@ pub struct _cef_cookie_visitor_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_cookie_visitor_t = _cef_cookie_visitor_t;
 
@@ -480,7 +493,8 @@ pub struct CefCookieVisitor {
 impl Clone for CefCookieVisitor {
   fn clone(&self) -> CefCookieVisitor{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefCookieVisitor {
@@ -493,7 +507,8 @@ impl Clone for CefCookieVisitor {
 impl Drop for CefCookieVisitor {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -508,7 +523,8 @@ impl CefCookieVisitor {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_cookie_visitor_t) -> CefCookieVisitor {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefCookieVisitor {
@@ -522,7 +538,8 @@ impl CefCookieVisitor {
 
   pub fn c_object_addrefed(&self) -> *mut cef_cookie_visitor_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -530,10 +547,10 @@ impl CefCookieVisitor {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -545,7 +562,8 @@ impl CefCookieVisitor {
   //
   pub fn visit(&self, cookie: &interfaces::CefCookie, count: libc::c_int,
       total: libc::c_int, deleteCookie: &mut libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -576,7 +594,8 @@ impl CefWrap<*mut cef_cookie_visitor_t> for Option<CefCookieVisitor> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_cookie_visitor_t) -> Option<CefCookieVisitor> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefCookieVisitor::from_c_object_addref(c_object))
@@ -606,13 +625,13 @@ pub struct _cef_set_cookie_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_set_cookie_callback_t = _cef_set_cookie_callback_t;
 
@@ -628,7 +647,8 @@ pub struct CefSetCookieCallback {
 impl Clone for CefSetCookieCallback {
   fn clone(&self) -> CefSetCookieCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefSetCookieCallback {
@@ -641,7 +661,8 @@ impl Clone for CefSetCookieCallback {
 impl Drop for CefSetCookieCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -656,7 +677,8 @@ impl CefSetCookieCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_set_cookie_callback_t) -> CefSetCookieCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefSetCookieCallback {
@@ -670,7 +692,8 @@ impl CefSetCookieCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_set_cookie_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -678,10 +701,10 @@ impl CefSetCookieCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -689,7 +712,8 @@ impl CefSetCookieCallback {
   // the cookie was set successfully.
   //
   pub fn on_complete(&self, success: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -717,7 +741,8 @@ impl CefWrap<*mut cef_set_cookie_callback_t> for Option<CefSetCookieCallback> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_set_cookie_callback_t) -> Option<CefSetCookieCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefSetCookieCallback::from_c_object_addref(c_object))
@@ -748,13 +773,13 @@ pub struct _cef_delete_cookies_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_delete_cookies_callback_t = _cef_delete_cookies_callback_t;
 
@@ -770,7 +795,8 @@ pub struct CefDeleteCookiesCallback {
 impl Clone for CefDeleteCookiesCallback {
   fn clone(&self) -> CefDeleteCookiesCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefDeleteCookiesCallback {
@@ -783,7 +809,8 @@ impl Clone for CefDeleteCookiesCallback {
 impl Drop for CefDeleteCookiesCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -798,7 +825,8 @@ impl CefDeleteCookiesCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_delete_cookies_callback_t) -> CefDeleteCookiesCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefDeleteCookiesCallback {
@@ -812,7 +840,8 @@ impl CefDeleteCookiesCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_delete_cookies_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -820,10 +849,10 @@ impl CefDeleteCookiesCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -831,7 +860,8 @@ impl CefDeleteCookiesCallback {
   // number of cookies that were deleted or -1 if unknown.
   //
   pub fn on_complete(&self, num_deleted: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -859,7 +889,8 @@ impl CefWrap<*mut cef_delete_cookies_callback_t> for Option<CefDeleteCookiesCall
     }
   }
   unsafe fn to_rust(c_object: *mut cef_delete_cookies_callback_t) -> Option<CefDeleteCookiesCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefDeleteCookiesCallback::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_dialog_handler.rs b/ports/cef/interfaces/cef_dialog_handler.rs
index d6db8bfd7f6..c64634e061e 100644
--- a/ports/cef/interfaces/cef_dialog_handler.rs
+++ b/ports/cef/interfaces/cef_dialog_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -75,13 +76,13 @@ pub struct _cef_file_dialog_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_file_dialog_callback_t = _cef_file_dialog_callback_t;
 
@@ -96,7 +97,8 @@ pub struct CefFileDialogCallback {
 impl Clone for CefFileDialogCallback {
   fn clone(&self) -> CefFileDialogCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefFileDialogCallback {
@@ -109,7 +111,8 @@ impl Clone for CefFileDialogCallback {
 impl Drop for CefFileDialogCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -124,7 +127,8 @@ impl CefFileDialogCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_file_dialog_callback_t) -> CefFileDialogCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefFileDialogCallback {
@@ -138,7 +142,8 @@ impl CefFileDialogCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_file_dialog_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -146,10 +151,10 @@ impl CefFileDialogCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -161,7 +166,8 @@ impl CefFileDialogCallback {
   //
   pub fn cont(&self, selected_accept_filter: libc::c_int,
       file_paths: Vec<String>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -177,7 +183,8 @@ impl CefFileDialogCallback {
   // Cancel the file selection.
   //
   pub fn cancel(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -204,7 +211,8 @@ impl CefWrap<*mut cef_file_dialog_callback_t> for Option<CefFileDialogCallback>
     }
   }
   unsafe fn to_rust(c_object: *mut cef_file_dialog_callback_t) -> Option<CefFileDialogCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefFileDialogCallback::from_c_object_addref(c_object))
@@ -250,13 +258,13 @@ pub struct _cef_dialog_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_dialog_handler_t = _cef_dialog_handler_t;
 
@@ -272,7 +280,8 @@ pub struct CefDialogHandler {
 impl Clone for CefDialogHandler {
   fn clone(&self) -> CefDialogHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefDialogHandler {
@@ -285,7 +294,8 @@ impl Clone for CefDialogHandler {
 impl Drop for CefDialogHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -300,7 +310,8 @@ impl CefDialogHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_dialog_handler_t) -> CefDialogHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefDialogHandler {
@@ -314,7 +325,8 @@ impl CefDialogHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_dialog_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -322,10 +334,10 @@ impl CefDialogHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -348,7 +360,8 @@ impl CefDialogHandler {
       default_file_path: &[u16], accept_filters: Vec<String>,
       selected_accept_filter: libc::c_int,
       callback: interfaces::CefFileDialogCallback) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -382,7 +395,8 @@ impl CefWrap<*mut cef_dialog_handler_t> for Option<CefDialogHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_dialog_handler_t) -> Option<CefDialogHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefDialogHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_display_handler.rs b/ports/cef/interfaces/cef_display_handler.rs
index 6bfc68d1ca4..1221e0e3889 100644
--- a/ports/cef/interfaces/cef_display_handler.rs
+++ b/ports/cef/interfaces/cef_display_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -110,13 +111,13 @@ pub struct _cef_display_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_display_handler_t = _cef_display_handler_t;
 
@@ -132,7 +133,8 @@ pub struct CefDisplayHandler {
 impl Clone for CefDisplayHandler {
   fn clone(&self) -> CefDisplayHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefDisplayHandler {
@@ -145,7 +147,8 @@ impl Clone for CefDisplayHandler {
 impl Drop for CefDisplayHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -160,7 +163,8 @@ impl CefDisplayHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_display_handler_t) -> CefDisplayHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefDisplayHandler {
@@ -174,7 +178,8 @@ impl CefDisplayHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_display_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -182,10 +187,10 @@ impl CefDisplayHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -193,7 +198,8 @@ impl CefDisplayHandler {
   //
   pub fn on_address_change(&self, browser: interfaces::CefBrowser,
       frame: interfaces::CefFrame, url: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -211,7 +217,8 @@ impl CefDisplayHandler {
   //
   pub fn on_title_change(&self, browser: interfaces::CefBrowser,
       title: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -228,7 +235,8 @@ impl CefDisplayHandler {
   //
   pub fn on_favicon_urlchange(&self, browser: interfaces::CefBrowser,
       icon_urls: Vec<String>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -250,7 +258,8 @@ impl CefDisplayHandler {
   //
   pub fn on_tooltip(&self, browser: interfaces::CefBrowser,
       text: *mut types::cef_string_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -268,7 +277,8 @@ impl CefDisplayHandler {
   //
   pub fn on_status_message(&self, browser: interfaces::CefBrowser,
       value: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -286,7 +296,8 @@ impl CefDisplayHandler {
   //
   pub fn on_console_message(&self, browser: interfaces::CefBrowser,
       message: &[u16], source: &[u16], line: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -317,7 +328,8 @@ impl CefWrap<*mut cef_display_handler_t> for Option<CefDisplayHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_display_handler_t) -> Option<CefDisplayHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefDisplayHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_dom.rs b/ports/cef/interfaces/cef_dom.rs
index c12fde98f47..6fc2f880675 100644
--- a/ports/cef/interfaces/cef_dom.rs
+++ b/ports/cef/interfaces/cef_dom.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -69,13 +70,13 @@ pub struct _cef_domvisitor_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_domvisitor_t = _cef_domvisitor_t;
 
@@ -91,7 +92,8 @@ pub struct CefDOMVisitor {
 impl Clone for CefDOMVisitor {
   fn clone(&self) -> CefDOMVisitor{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefDOMVisitor {
@@ -104,7 +106,8 @@ impl Clone for CefDOMVisitor {
 impl Drop for CefDOMVisitor {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -119,7 +122,8 @@ impl CefDOMVisitor {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_domvisitor_t) -> CefDOMVisitor {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefDOMVisitor {
@@ -133,7 +137,8 @@ impl CefDOMVisitor {
 
   pub fn c_object_addrefed(&self) -> *mut cef_domvisitor_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -141,10 +146,10 @@ impl CefDOMVisitor {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -155,7 +160,8 @@ impl CefDOMVisitor {
   // of this function.
   //
   pub fn visit(&self, document: interfaces::CefDOMDocument) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -183,7 +189,8 @@ impl CefWrap<*mut cef_domvisitor_t> for Option<CefDOMVisitor> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_domvisitor_t) -> Option<CefDOMVisitor> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefDOMVisitor::from_c_object_addref(c_object))
@@ -296,13 +303,13 @@ pub struct _cef_domdocument_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_domdocument_t = _cef_domdocument_t;
 
@@ -318,7 +325,8 @@ pub struct CefDOMDocument {
 impl Clone for CefDOMDocument {
   fn clone(&self) -> CefDOMDocument{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefDOMDocument {
@@ -331,7 +339,8 @@ impl Clone for CefDOMDocument {
 impl Drop for CefDOMDocument {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -346,7 +355,8 @@ impl CefDOMDocument {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_domdocument_t) -> CefDOMDocument {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefDOMDocument {
@@ -360,7 +370,8 @@ impl CefDOMDocument {
 
   pub fn c_object_addrefed(&self) -> *mut cef_domdocument_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -368,17 +379,18 @@ impl CefDOMDocument {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Returns the document type.
   //
   pub fn get_type(&self) -> types::cef_dom_document_type_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -392,7 +404,8 @@ impl CefDOMDocument {
   // Returns the root document node.
   //
   pub fn get_document(&self) -> interfaces::CefDOMNode {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -406,7 +419,8 @@ impl CefDOMDocument {
   // Returns the BODY node of an HTML document.
   //
   pub fn get_body(&self) -> interfaces::CefDOMNode {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -420,7 +434,8 @@ impl CefDOMDocument {
   // Returns the HEAD node of an HTML document.
   //
   pub fn get_head(&self) -> interfaces::CefDOMNode {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -435,7 +450,8 @@ impl CefDOMDocument {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_title(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -449,7 +465,8 @@ impl CefDOMDocument {
   // Returns the document element with the specified ID value.
   //
   pub fn get_element_by_id(&self, id: &[u16]) -> interfaces::CefDOMNode {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -464,7 +481,8 @@ impl CefDOMDocument {
   // Returns the node that currently has keyboard focus.
   //
   pub fn get_focused_node(&self) -> interfaces::CefDOMNode {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -478,7 +496,8 @@ impl CefDOMDocument {
   // Returns true (1) if a portion of the document is selected.
   //
   pub fn has_selection(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -492,7 +511,8 @@ impl CefDOMDocument {
   // Returns the selection offset within the start node.
   //
   pub fn get_selection_start_offset(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -506,7 +526,8 @@ impl CefDOMDocument {
   // Returns the selection offset within the end node.
   //
   pub fn get_selection_end_offset(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -521,7 +542,8 @@ impl CefDOMDocument {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_selection_as_markup(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -536,7 +558,8 @@ impl CefDOMDocument {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_selection_as_text(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -551,7 +574,8 @@ impl CefDOMDocument {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_base_url(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -567,7 +591,8 @@ impl CefDOMDocument {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_complete_url(&self, partialURL: &[u16]) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -595,7 +620,8 @@ impl CefWrap<*mut cef_domdocument_t> for Option<CefDOMDocument> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_domdocument_t) -> Option<CefDOMDocument> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefDOMDocument::from_c_object_addref(c_object))
@@ -780,13 +806,13 @@ pub struct _cef_domnode_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_domnode_t = _cef_domnode_t;
 
@@ -802,7 +828,8 @@ pub struct CefDOMNode {
 impl Clone for CefDOMNode {
   fn clone(&self) -> CefDOMNode{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefDOMNode {
@@ -815,7 +842,8 @@ impl Clone for CefDOMNode {
 impl Drop for CefDOMNode {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -830,7 +858,8 @@ impl CefDOMNode {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_domnode_t) -> CefDOMNode {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefDOMNode {
@@ -844,7 +873,8 @@ impl CefDOMNode {
 
   pub fn c_object_addrefed(&self) -> *mut cef_domnode_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -852,17 +882,18 @@ impl CefDOMNode {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Returns the type for this node.
   //
   pub fn get_type(&self) -> types::cef_dom_node_type_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -876,7 +907,8 @@ impl CefDOMNode {
   // Returns true (1) if this is a text node.
   //
   pub fn is_text(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -890,7 +922,8 @@ impl CefDOMNode {
   // Returns true (1) if this is an element node.
   //
   pub fn is_element(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -904,7 +937,8 @@ impl CefDOMNode {
   // Returns true (1) if this is an editable node.
   //
   pub fn is_editable(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -918,7 +952,8 @@ impl CefDOMNode {
   // Returns true (1) if this is a form control element node.
   //
   pub fn is_form_control_element(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -933,7 +968,8 @@ impl CefDOMNode {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_form_control_element_type(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -948,7 +984,8 @@ impl CefDOMNode {
   // object.
   //
   pub fn is_same(&self, that: interfaces::CefDOMNode) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -964,7 +1001,8 @@ impl CefDOMNode {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -979,7 +1017,8 @@ impl CefDOMNode {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_value(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -993,7 +1032,8 @@ impl CefDOMNode {
   // Set the value of this node. Returns true (1) on success.
   //
   pub fn set_value(&self, value: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1009,7 +1049,8 @@ impl CefDOMNode {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_as_markup(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1023,7 +1064,8 @@ impl CefDOMNode {
   // Returns the document associated with this node.
   //
   pub fn get_document(&self) -> interfaces::CefDOMDocument {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1037,7 +1079,8 @@ impl CefDOMNode {
   // Returns the parent node.
   //
   pub fn get_parent(&self) -> interfaces::CefDOMNode {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1051,7 +1094,8 @@ impl CefDOMNode {
   // Returns the previous sibling node.
   //
   pub fn get_previous_sibling(&self) -> interfaces::CefDOMNode {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1065,7 +1109,8 @@ impl CefDOMNode {
   // Returns the next sibling node.
   //
   pub fn get_next_sibling(&self) -> interfaces::CefDOMNode {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1079,7 +1124,8 @@ impl CefDOMNode {
   // Returns true (1) if this node has child nodes.
   //
   pub fn has_children(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1093,7 +1139,8 @@ impl CefDOMNode {
   // Return the first child node.
   //
   pub fn get_first_child(&self) -> interfaces::CefDOMNode {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1107,7 +1154,8 @@ impl CefDOMNode {
   // Returns the last child node.
   //
   pub fn get_last_child(&self) -> interfaces::CefDOMNode {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1125,7 +1173,8 @@ impl CefDOMNode {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_element_tag_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1139,7 +1188,8 @@ impl CefDOMNode {
   // Returns true (1) if this element has attributes.
   //
   pub fn has_element_attributes(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1153,7 +1203,8 @@ impl CefDOMNode {
   // Returns true (1) if this element has an attribute named |attrName|.
   //
   pub fn has_element_attribute(&self, attrName: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1169,7 +1220,8 @@ impl CefDOMNode {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_element_attribute(&self, attrName: &[u16]) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1184,7 +1236,8 @@ impl CefDOMNode {
   // Returns a map of all element attributes.
   //
   pub fn get_element_attributes(&self, attrMap: HashMap<String,String>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1201,7 +1254,8 @@ impl CefDOMNode {
   //
   pub fn set_element_attribute(&self, attrName: &[u16],
       value: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1218,7 +1272,8 @@ impl CefDOMNode {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_element_inner_text(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1245,7 +1300,8 @@ impl CefWrap<*mut cef_domnode_t> for Option<CefDOMNode> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_domnode_t) -> Option<CefDOMNode> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefDOMNode::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_download_handler.rs b/ports/cef/interfaces/cef_download_handler.rs
index 8555f0435a4..7dce76b2ae0 100644
--- a/ports/cef/interfaces/cef_download_handler.rs
+++ b/ports/cef/interfaces/cef_download_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -68,13 +69,13 @@ pub struct _cef_before_download_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_before_download_callback_t = _cef_before_download_callback_t;
 
@@ -89,7 +90,8 @@ pub struct CefBeforeDownloadCallback {
 impl Clone for CefBeforeDownloadCallback {
   fn clone(&self) -> CefBeforeDownloadCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefBeforeDownloadCallback {
@@ -102,7 +104,8 @@ impl Clone for CefBeforeDownloadCallback {
 impl Drop for CefBeforeDownloadCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -117,7 +120,8 @@ impl CefBeforeDownloadCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_before_download_callback_t) -> CefBeforeDownloadCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefBeforeDownloadCallback {
@@ -131,7 +135,8 @@ impl CefBeforeDownloadCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_before_download_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -139,10 +144,10 @@ impl CefBeforeDownloadCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -152,7 +157,8 @@ impl CefBeforeDownloadCallback {
   // (1) if you do wish to show the default "Save As" dialog.
   //
   pub fn cont(&self, download_path: &[u16], show_dialog: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -181,7 +187,8 @@ impl CefWrap<*mut cef_before_download_callback_t> for Option<CefBeforeDownloadCa
     }
   }
   unsafe fn to_rust(c_object: *mut cef_before_download_callback_t) -> Option<CefBeforeDownloadCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefBeforeDownloadCallback::from_c_object_addref(c_object))
@@ -221,13 +228,13 @@ pub struct _cef_download_item_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_download_item_callback_t = _cef_download_item_callback_t;
 
@@ -242,7 +249,8 @@ pub struct CefDownloadItemCallback {
 impl Clone for CefDownloadItemCallback {
   fn clone(&self) -> CefDownloadItemCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefDownloadItemCallback {
@@ -255,7 +263,8 @@ impl Clone for CefDownloadItemCallback {
 impl Drop for CefDownloadItemCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -270,7 +279,8 @@ impl CefDownloadItemCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_download_item_callback_t) -> CefDownloadItemCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefDownloadItemCallback {
@@ -284,7 +294,8 @@ impl CefDownloadItemCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_download_item_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -292,17 +303,18 @@ impl CefDownloadItemCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Call to cancel the download.
   //
   pub fn cancel(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -316,7 +328,8 @@ impl CefDownloadItemCallback {
   // Call to pause the download.
   //
   pub fn pause(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -330,7 +343,8 @@ impl CefDownloadItemCallback {
   // Call to resume the download.
   //
   pub fn resume(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -357,7 +371,8 @@ impl CefWrap<*mut cef_download_item_callback_t> for Option<CefDownloadItemCallba
     }
   }
   unsafe fn to_rust(c_object: *mut cef_download_item_callback_t) -> Option<CefDownloadItemCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefDownloadItemCallback::from_c_object_addref(c_object))
@@ -407,13 +422,13 @@ pub struct _cef_download_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_download_handler_t = _cef_download_handler_t;
 
@@ -429,7 +444,8 @@ pub struct CefDownloadHandler {
 impl Clone for CefDownloadHandler {
   fn clone(&self) -> CefDownloadHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefDownloadHandler {
@@ -442,7 +458,8 @@ impl Clone for CefDownloadHandler {
 impl Drop for CefDownloadHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -457,7 +474,8 @@ impl CefDownloadHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_download_handler_t) -> CefDownloadHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefDownloadHandler {
@@ -471,7 +489,8 @@ impl CefDownloadHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_download_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -479,10 +498,10 @@ impl CefDownloadHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -495,7 +514,8 @@ impl CefDownloadHandler {
   pub fn on_before_download(&self, browser: interfaces::CefBrowser,
       download_item: interfaces::CefDownloadItem, suggested_name: &[u16],
       callback: interfaces::CefBeforeDownloadCallback) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -519,7 +539,8 @@ impl CefDownloadHandler {
   pub fn on_download_updated(&self, browser: interfaces::CefBrowser,
       download_item: interfaces::CefDownloadItem,
       callback: interfaces::CefDownloadItemCallback) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -549,7 +570,8 @@ impl CefWrap<*mut cef_download_handler_t> for Option<CefDownloadHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_download_handler_t) -> Option<CefDownloadHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefDownloadHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_download_item.rs b/ports/cef/interfaces/cef_download_item.rs
index 55513327f74..88ca0fc16d9 100644
--- a/ports/cef/interfaces/cef_download_item.rs
+++ b/ports/cef/interfaces/cef_download_item.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -167,13 +168,13 @@ pub struct _cef_download_item_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_download_item_t = _cef_download_item_t;
 
@@ -188,7 +189,8 @@ pub struct CefDownloadItem {
 impl Clone for CefDownloadItem {
   fn clone(&self) -> CefDownloadItem{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefDownloadItem {
@@ -201,7 +203,8 @@ impl Clone for CefDownloadItem {
 impl Drop for CefDownloadItem {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -216,7 +219,8 @@ impl CefDownloadItem {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_download_item_t) -> CefDownloadItem {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefDownloadItem {
@@ -230,7 +234,8 @@ impl CefDownloadItem {
 
   pub fn c_object_addrefed(&self) -> *mut cef_download_item_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -238,10 +243,10 @@ impl CefDownloadItem {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -249,7 +254,8 @@ impl CefDownloadItem {
   // if this function returns false (0).
   //
   pub fn is_valid(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -263,7 +269,8 @@ impl CefDownloadItem {
   // Returns true (1) if the download is in progress.
   //
   pub fn is_in_progress(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -277,7 +284,8 @@ impl CefDownloadItem {
   // Returns true (1) if the download is complete.
   //
   pub fn is_complete(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -291,7 +299,8 @@ impl CefDownloadItem {
   // Returns true (1) if the download has been canceled or interrupted.
   //
   pub fn is_canceled(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -305,7 +314,8 @@ impl CefDownloadItem {
   // Returns a simple speed estimate in bytes/s.
   //
   pub fn get_current_speed(&self) -> i64 {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -320,7 +330,8 @@ impl CefDownloadItem {
   // unknown.
   //
   pub fn get_percent_complete(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -334,7 +345,8 @@ impl CefDownloadItem {
   // Returns the total number of bytes.
   //
   pub fn get_total_bytes(&self) -> i64 {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -348,7 +360,8 @@ impl CefDownloadItem {
   // Returns the number of received bytes.
   //
   pub fn get_received_bytes(&self) -> i64 {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -362,7 +375,8 @@ impl CefDownloadItem {
   // Returns the time that the download started.
   //
   pub fn get_start_time(&self) -> types::cef_time_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -376,7 +390,8 @@ impl CefDownloadItem {
   // Returns the time that the download ended.
   //
   pub fn get_end_time(&self) -> types::cef_time_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -391,7 +406,8 @@ impl CefDownloadItem {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_full_path(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -405,7 +421,8 @@ impl CefDownloadItem {
   // Returns the unique identifier for this download.
   //
   pub fn get_id(&self) -> u32 {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -420,7 +437,8 @@ impl CefDownloadItem {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_url(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -435,7 +453,8 @@ impl CefDownloadItem {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_original_url(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -450,7 +469,8 @@ impl CefDownloadItem {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_suggested_file_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -465,7 +485,8 @@ impl CefDownloadItem {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_content_disposition(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -480,7 +501,8 @@ impl CefDownloadItem {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_mime_type(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -507,7 +529,8 @@ impl CefWrap<*mut cef_download_item_t> for Option<CefDownloadItem> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_download_item_t) -> Option<CefDownloadItem> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefDownloadItem::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_drag_data.rs b/ports/cef/interfaces/cef_drag_data.rs
index 5983a7a7098..2c4d3ec1349 100644
--- a/ports/cef/interfaces/cef_drag_data.rs
+++ b/ports/cef/interfaces/cef_drag_data.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -204,13 +205,13 @@ pub struct _cef_drag_data_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_drag_data_t = _cef_drag_data_t;
 
@@ -226,7 +227,8 @@ pub struct CefDragData {
 impl Clone for CefDragData {
   fn clone(&self) -> CefDragData{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefDragData {
@@ -239,7 +241,8 @@ impl Clone for CefDragData {
 impl Drop for CefDragData {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -254,7 +257,8 @@ impl CefDragData {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_drag_data_t) -> CefDragData {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefDragData {
@@ -268,7 +272,8 @@ impl CefDragData {
 
   pub fn c_object_addrefed(&self) -> *mut cef_drag_data_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -276,17 +281,18 @@ impl CefDragData {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Returns a copy of the current object.
   //
   pub fn clone(&self) -> interfaces::CefDragData {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -300,7 +306,8 @@ impl CefDragData {
   // Returns true (1) if this object is read-only.
   //
   pub fn is_read_only(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -314,7 +321,8 @@ impl CefDragData {
   // Returns true (1) if the drag data is a link.
   //
   pub fn is_link(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -328,7 +336,8 @@ impl CefDragData {
   // Returns true (1) if the drag data is a text or html fragment.
   //
   pub fn is_fragment(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -342,7 +351,8 @@ impl CefDragData {
   // Returns true (1) if the drag data is a file.
   //
   pub fn is_file(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -357,7 +367,8 @@ impl CefDragData {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_link_url(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -372,7 +383,8 @@ impl CefDragData {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_link_title(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -387,7 +399,8 @@ impl CefDragData {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_link_metadata(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -402,7 +415,8 @@ impl CefDragData {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_fragment_text(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -417,7 +431,8 @@ impl CefDragData {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_fragment_html(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -433,7 +448,8 @@ impl CefDragData {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_fragment_base_url(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -448,7 +464,8 @@ impl CefDragData {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_file_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -466,7 +483,8 @@ impl CefDragData {
   //
   pub fn get_file_contents(&self,
       writer: interfaces::CefStreamWriter) -> libc::size_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -482,7 +500,8 @@ impl CefDragData {
   // window.
   //
   pub fn get_file_names(&self, names: Vec<String>) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -497,7 +516,8 @@ impl CefDragData {
   // Set the link URL that is being dragged.
   //
   pub fn set_link_url(&self, url: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -512,7 +532,8 @@ impl CefDragData {
   // Set the title associated with the link being dragged.
   //
   pub fn set_link_title(&self, title: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -527,7 +548,8 @@ impl CefDragData {
   // Set the metadata associated with the link being dragged.
   //
   pub fn set_link_metadata(&self, data: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -542,7 +564,8 @@ impl CefDragData {
   // Set the plain text fragment that is being dragged.
   //
   pub fn set_fragment_text(&self, text: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -557,7 +580,8 @@ impl CefDragData {
   // Set the text/html fragment that is being dragged.
   //
   pub fn set_fragment_html(&self, html: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -572,7 +596,8 @@ impl CefDragData {
   // Set the base URL that the fragment came from.
   //
   pub fn set_fragment_base_url(&self, base_url: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -589,7 +614,8 @@ impl CefDragData {
   // to drag in this kind of data.
   //
   pub fn reset_file_contents(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -603,7 +629,8 @@ impl CefDragData {
   // Add a file that is being dragged into the webview.
   //
   pub fn add_file(&self, path: &[u16], display_name: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -643,7 +670,8 @@ impl CefWrap<*mut cef_drag_data_t> for Option<CefDragData> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_drag_data_t) -> Option<CefDragData> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefDragData::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_drag_handler.rs b/ports/cef/interfaces/cef_drag_handler.rs
index 6236a11056b..15fd7f37d8f 100644
--- a/ports/cef/interfaces/cef_drag_handler.rs
+++ b/ports/cef/interfaces/cef_drag_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -70,13 +71,13 @@ pub struct _cef_drag_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_drag_handler_t = _cef_drag_handler_t;
 
@@ -92,7 +93,8 @@ pub struct CefDragHandler {
 impl Clone for CefDragHandler {
   fn clone(&self) -> CefDragHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefDragHandler {
@@ -105,7 +107,8 @@ impl Clone for CefDragHandler {
 impl Drop for CefDragHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -120,7 +123,8 @@ impl CefDragHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_drag_handler_t) -> CefDragHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefDragHandler {
@@ -134,7 +138,8 @@ impl CefDragHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_drag_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -142,10 +147,10 @@ impl CefDragHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -157,7 +162,8 @@ impl CefDragHandler {
   pub fn on_drag_enter(&self, browser: interfaces::CefBrowser,
       dragData: interfaces::CefDragData,
       mask: types::cef_drag_operations_mask_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -187,7 +193,8 @@ impl CefWrap<*mut cef_drag_handler_t> for Option<CefDragHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_drag_handler_t) -> Option<CefDragHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefDragHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_find_handler.rs b/ports/cef/interfaces/cef_find_handler.rs
index b1afd79ff11..05155095451 100644
--- a/ports/cef/interfaces/cef_find_handler.rs
+++ b/ports/cef/interfaces/cef_find_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -72,13 +73,13 @@ pub struct _cef_find_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_find_handler_t = _cef_find_handler_t;
 
@@ -94,7 +95,8 @@ pub struct CefFindHandler {
 impl Clone for CefFindHandler {
   fn clone(&self) -> CefFindHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefFindHandler {
@@ -107,7 +109,8 @@ impl Clone for CefFindHandler {
 impl Drop for CefFindHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -122,7 +125,8 @@ impl CefFindHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_find_handler_t) -> CefFindHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefFindHandler {
@@ -136,7 +140,8 @@ impl CefFindHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_find_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -144,10 +149,10 @@ impl CefFindHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -162,7 +167,8 @@ impl CefFindHandler {
       identifier: libc::c_int, count: libc::c_int,
       selectionRect: &types::cef_rect_t, activeMatchOrdinal: libc::c_int,
       finalUpdate: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -195,7 +201,8 @@ impl CefWrap<*mut cef_find_handler_t> for Option<CefFindHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_find_handler_t) -> Option<CefFindHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefFindHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_focus_handler.rs b/ports/cef/interfaces/cef_focus_handler.rs
index 6695253dbb4..b5d1d6072b0 100644
--- a/ports/cef/interfaces/cef_focus_handler.rs
+++ b/ports/cef/interfaces/cef_focus_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -83,13 +84,13 @@ pub struct _cef_focus_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_focus_handler_t = _cef_focus_handler_t;
 
@@ -105,7 +106,8 @@ pub struct CefFocusHandler {
 impl Clone for CefFocusHandler {
   fn clone(&self) -> CefFocusHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefFocusHandler {
@@ -118,7 +120,8 @@ impl Clone for CefFocusHandler {
 impl Drop for CefFocusHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -133,7 +136,8 @@ impl CefFocusHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_focus_handler_t) -> CefFocusHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefFocusHandler {
@@ -147,7 +151,8 @@ impl CefFocusHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_focus_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -155,10 +160,10 @@ impl CefFocusHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -169,7 +174,8 @@ impl CefFocusHandler {
   //
   pub fn on_take_focus(&self, browser: interfaces::CefBrowser,
       next: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -188,7 +194,8 @@ impl CefFocusHandler {
   //
   pub fn on_set_focus(&self, browser: interfaces::CefBrowser,
       source: types::cef_focus_source_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -204,7 +211,8 @@ impl CefFocusHandler {
   // Called when the browser component has received focus.
   //
   pub fn on_got_focus(&self, browser: interfaces::CefBrowser) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -232,7 +240,8 @@ impl CefWrap<*mut cef_focus_handler_t> for Option<CefFocusHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_focus_handler_t) -> Option<CefFocusHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefFocusHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_frame.rs b/ports/cef/interfaces/cef_frame.rs
index 0ba77018d20..62fa1bb8d0e 100644
--- a/ports/cef/interfaces/cef_frame.rs
+++ b/ports/cef/interfaces/cef_frame.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -214,13 +215,13 @@ pub struct _cef_frame_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_frame_t = _cef_frame_t;
 
@@ -238,7 +239,8 @@ pub struct CefFrame {
 impl Clone for CefFrame {
   fn clone(&self) -> CefFrame{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefFrame {
@@ -251,7 +253,8 @@ impl Clone for CefFrame {
 impl Drop for CefFrame {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -266,7 +269,8 @@ impl CefFrame {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_frame_t) -> CefFrame {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefFrame {
@@ -280,7 +284,8 @@ impl CefFrame {
 
   pub fn c_object_addrefed(&self) -> *mut cef_frame_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -288,17 +293,18 @@ impl CefFrame {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // True if this object is currently attached to a valid frame.
   //
   pub fn is_valid(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -312,7 +318,8 @@ impl CefFrame {
   // Execute undo in this frame.
   //
   pub fn undo(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -326,7 +333,8 @@ impl CefFrame {
   // Execute redo in this frame.
   //
   pub fn redo(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -340,7 +348,8 @@ impl CefFrame {
   // Execute cut in this frame.
   //
   pub fn cut(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -354,7 +363,8 @@ impl CefFrame {
   // Execute copy in this frame.
   //
   pub fn copy(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -368,7 +378,8 @@ impl CefFrame {
   // Execute paste in this frame.
   //
   pub fn paste(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -382,7 +393,8 @@ impl CefFrame {
   // Execute delete in this frame.
   //
   pub fn del(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -396,7 +408,8 @@ impl CefFrame {
   // Execute select all in this frame.
   //
   pub fn select_all(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -412,7 +425,8 @@ impl CefFrame {
   // browser process.
   //
   pub fn view_source(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -427,7 +441,8 @@ impl CefFrame {
   // visitor.
   //
   pub fn get_source(&self, visitor: interfaces::CefStringVisitor) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -443,7 +458,8 @@ impl CefFrame {
   // visitor.
   //
   pub fn get_text(&self, visitor: interfaces::CefStringVisitor) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -458,7 +474,8 @@ impl CefFrame {
   // Load the request represented by the |request| object.
   //
   pub fn load_request(&self, request: interfaces::CefRequest) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -473,7 +490,8 @@ impl CefFrame {
   // Load the specified |url|.
   //
   pub fn load_url(&self, url: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -490,7 +508,8 @@ impl CefFrame {
   // link clicks and web security restrictions may not behave as expected.
   //
   pub fn load_string(&self, string_val: &[u16], url: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -511,7 +530,8 @@ impl CefFrame {
   //
   pub fn execute_java_script(&self, code: &[u16], script_url: &[u16],
       start_line: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -528,7 +548,8 @@ impl CefFrame {
   // Returns true (1) if this is the main (top-level) frame.
   //
   pub fn is_main(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -542,7 +563,8 @@ impl CefFrame {
   // Returns true (1) if this is the focused frame.
   //
   pub fn is_focused(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -561,7 +583,8 @@ impl CefFrame {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -575,7 +598,8 @@ impl CefFrame {
   // Returns the globally unique identifier for this frame.
   //
   pub fn get_identifier(&self) -> i64 {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -590,7 +614,8 @@ impl CefFrame {
   // frame.
   //
   pub fn get_parent(&self) -> interfaces::CefFrame {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -605,7 +630,8 @@ impl CefFrame {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_url(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -619,7 +645,8 @@ impl CefFrame {
   // Returns the browser that this frame belongs to.
   //
   pub fn get_browser(&self) -> interfaces::CefBrowser {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -634,7 +661,8 @@ impl CefFrame {
   // called from the render process.
   //
   pub fn get_v8context(&self) -> interfaces::CefV8Context {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -649,7 +677,8 @@ impl CefFrame {
   // process.
   //
   pub fn visit_dom(&self, visitor: interfaces::CefDOMVisitor) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -677,7 +706,8 @@ impl CefWrap<*mut cef_frame_t> for Option<CefFrame> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_frame_t) -> Option<CefFrame> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefFrame::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_geolocation.rs b/ports/cef/interfaces/cef_geolocation.rs
index 8ef1072a103..0b4b54a3daa 100644
--- a/ports/cef/interfaces/cef_geolocation.rs
+++ b/ports/cef/interfaces/cef_geolocation.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -67,13 +68,13 @@ pub struct _cef_get_geolocation_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_get_geolocation_callback_t = _cef_get_geolocation_callback_t;
 
@@ -89,7 +90,8 @@ pub struct CefGetGeolocationCallback {
 impl Clone for CefGetGeolocationCallback {
   fn clone(&self) -> CefGetGeolocationCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefGetGeolocationCallback {
@@ -102,7 +104,8 @@ impl Clone for CefGetGeolocationCallback {
 impl Drop for CefGetGeolocationCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -117,7 +120,8 @@ impl CefGetGeolocationCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_get_geolocation_callback_t) -> CefGetGeolocationCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefGetGeolocationCallback {
@@ -131,7 +135,8 @@ impl CefGetGeolocationCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_get_geolocation_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -139,10 +144,10 @@ impl CefGetGeolocationCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -151,7 +156,8 @@ impl CefGetGeolocationCallback {
   //
   pub fn on_location_update(&self, position: &interfaces::CefGeoposition) -> (
       ) {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -179,7 +185,8 @@ impl CefWrap<*mut cef_get_geolocation_callback_t> for Option<CefGetGeolocationCa
     }
   }
   unsafe fn to_rust(c_object: *mut cef_get_geolocation_callback_t) -> Option<CefGetGeolocationCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefGetGeolocationCallback::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_geolocation_handler.rs b/ports/cef/interfaces/cef_geolocation_handler.rs
index a342fd274ac..5214a245c51 100644
--- a/ports/cef/interfaces/cef_geolocation_handler.rs
+++ b/ports/cef/interfaces/cef_geolocation_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -65,13 +66,13 @@ pub struct _cef_geolocation_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_geolocation_callback_t = _cef_geolocation_callback_t;
 
@@ -87,7 +88,8 @@ pub struct CefGeolocationCallback {
 impl Clone for CefGeolocationCallback {
   fn clone(&self) -> CefGeolocationCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefGeolocationCallback {
@@ -100,7 +102,8 @@ impl Clone for CefGeolocationCallback {
 impl Drop for CefGeolocationCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -115,7 +118,8 @@ impl CefGeolocationCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_geolocation_callback_t) -> CefGeolocationCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefGeolocationCallback {
@@ -129,7 +133,8 @@ impl CefGeolocationCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_geolocation_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -137,17 +142,18 @@ impl CefGeolocationCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Call to allow or deny geolocation access.
   //
   pub fn cont(&self, allow: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -175,7 +181,8 @@ impl CefWrap<*mut cef_geolocation_callback_t> for Option<CefGeolocationCallback>
     }
   }
   unsafe fn to_rust(c_object: *mut cef_geolocation_callback_t) -> Option<CefGeolocationCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefGeolocationCallback::from_c_object_addref(c_object))
@@ -224,13 +231,13 @@ pub struct _cef_geolocation_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_geolocation_handler_t = _cef_geolocation_handler_t;
 
@@ -247,7 +254,8 @@ pub struct CefGeolocationHandler {
 impl Clone for CefGeolocationHandler {
   fn clone(&self) -> CefGeolocationHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefGeolocationHandler {
@@ -260,7 +268,8 @@ impl Clone for CefGeolocationHandler {
 impl Drop for CefGeolocationHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -275,7 +284,8 @@ impl CefGeolocationHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_geolocation_handler_t) -> CefGeolocationHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefGeolocationHandler {
@@ -289,7 +299,8 @@ impl CefGeolocationHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_geolocation_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -297,10 +308,10 @@ impl CefGeolocationHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -315,7 +326,8 @@ impl CefGeolocationHandler {
       browser: interfaces::CefBrowser, requesting_url: &[u16],
       request_id: libc::c_int,
       callback: interfaces::CefGeolocationCallback) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -337,7 +349,8 @@ impl CefGeolocationHandler {
   pub fn on_cancel_geolocation_permission(&self,
       browser: interfaces::CefBrowser, requesting_url: &[u16],
       request_id: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -367,7 +380,8 @@ impl CefWrap<*mut cef_geolocation_handler_t> for Option<CefGeolocationHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_geolocation_handler_t) -> Option<CefGeolocationHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefGeolocationHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_jsdialog_handler.rs b/ports/cef/interfaces/cef_jsdialog_handler.rs
index 6519ca2302b..bdb24eb6abb 100644
--- a/ports/cef/interfaces/cef_jsdialog_handler.rs
+++ b/ports/cef/interfaces/cef_jsdialog_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -66,13 +67,13 @@ pub struct _cef_jsdialog_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_jsdialog_callback_t = _cef_jsdialog_callback_t;
 
@@ -88,7 +89,8 @@ pub struct CefJSDialogCallback {
 impl Clone for CefJSDialogCallback {
   fn clone(&self) -> CefJSDialogCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefJSDialogCallback {
@@ -101,7 +103,8 @@ impl Clone for CefJSDialogCallback {
 impl Drop for CefJSDialogCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -116,7 +119,8 @@ impl CefJSDialogCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_jsdialog_callback_t) -> CefJSDialogCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefJSDialogCallback {
@@ -130,7 +134,8 @@ impl CefJSDialogCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_jsdialog_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -138,10 +143,10 @@ impl CefJSDialogCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -149,7 +154,8 @@ impl CefJSDialogCallback {
   // was pressed. The |user_input| value should be specified for prompt dialogs.
   //
   pub fn cont(&self, success: libc::c_int, user_input: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -178,7 +184,8 @@ impl CefWrap<*mut cef_jsdialog_callback_t> for Option<CefJSDialogCallback> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_jsdialog_callback_t) -> Option<CefJSDialogCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefJSDialogCallback::from_c_object_addref(c_object))
@@ -255,13 +262,13 @@ pub struct _cef_jsdialog_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_jsdialog_handler_t = _cef_jsdialog_handler_t;
 
@@ -277,7 +284,8 @@ pub struct CefJSDialogHandler {
 impl Clone for CefJSDialogHandler {
   fn clone(&self) -> CefJSDialogHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefJSDialogHandler {
@@ -290,7 +298,8 @@ impl Clone for CefJSDialogHandler {
 impl Drop for CefJSDialogHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -305,7 +314,8 @@ impl CefJSDialogHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_jsdialog_handler_t) -> CefJSDialogHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefJSDialogHandler {
@@ -319,7 +329,8 @@ impl CefJSDialogHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_jsdialog_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -327,10 +338,10 @@ impl CefJSDialogHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -353,7 +364,8 @@ impl CefJSDialogHandler {
       message_text: &[u16], default_prompt_text: &[u16],
       callback: interfaces::CefJSDialogCallback,
       suppress_message: &mut libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -382,7 +394,8 @@ impl CefJSDialogHandler {
   pub fn on_before_unload_dialog(&self, browser: interfaces::CefBrowser,
       message_text: &[u16], is_reload: libc::c_int,
       callback: interfaces::CefJSDialogCallback) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -402,7 +415,8 @@ impl CefJSDialogHandler {
   // dialogs are currently pending.
   //
   pub fn on_reset_dialog_state(&self, browser: interfaces::CefBrowser) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -417,7 +431,8 @@ impl CefJSDialogHandler {
   // Called when the default implementation dialog is closed.
   //
   pub fn on_dialog_closed(&self, browser: interfaces::CefBrowser) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -445,7 +460,8 @@ impl CefWrap<*mut cef_jsdialog_handler_t> for Option<CefJSDialogHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_jsdialog_handler_t) -> Option<CefJSDialogHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefJSDialogHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_keyboard_handler.rs b/ports/cef/interfaces/cef_keyboard_handler.rs
index 898afec3832..88cf4f2a02b 100644
--- a/ports/cef/interfaces/cef_keyboard_handler.rs
+++ b/ports/cef/interfaces/cef_keyboard_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -81,13 +82,13 @@ pub struct _cef_keyboard_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_keyboard_handler_t = _cef_keyboard_handler_t;
 
@@ -103,7 +104,8 @@ pub struct CefKeyboardHandler {
 impl Clone for CefKeyboardHandler {
   fn clone(&self) -> CefKeyboardHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefKeyboardHandler {
@@ -116,7 +118,8 @@ impl Clone for CefKeyboardHandler {
 impl Drop for CefKeyboardHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -131,7 +134,8 @@ impl CefKeyboardHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_keyboard_handler_t) -> CefKeyboardHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefKeyboardHandler {
@@ -145,7 +149,8 @@ impl CefKeyboardHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_keyboard_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -153,10 +158,10 @@ impl CefKeyboardHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   // Called before a keyboard event is sent to the renderer. |event| contains
@@ -167,7 +172,8 @@ impl CefKeyboardHandler {
   pub fn on_pre_key_event(&self, browser: interfaces::CefBrowser,
       event: &interfaces::CefKeyEvent, os_event: types::cef_event_handle_t,
       is_keyboard_shortcut: &mut libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -190,7 +196,8 @@ impl CefKeyboardHandler {
   pub fn on_key_event(&self, browser: interfaces::CefBrowser,
       event: &interfaces::CefKeyEvent,
       os_event: types::cef_event_handle_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -220,7 +227,8 @@ impl CefWrap<*mut cef_keyboard_handler_t> for Option<CefKeyboardHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_keyboard_handler_t) -> Option<CefKeyboardHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefKeyboardHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_life_span_handler.rs b/ports/cef/interfaces/cef_life_span_handler.rs
index 92b19e06415..cf2da948869 100644
--- a/ports/cef/interfaces/cef_life_span_handler.rs
+++ b/ports/cef/interfaces/cef_life_span_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -175,13 +176,13 @@ pub struct _cef_life_span_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_life_span_handler_t = _cef_life_span_handler_t;
 
@@ -198,7 +199,8 @@ pub struct CefLifeSpanHandler {
 impl Clone for CefLifeSpanHandler {
   fn clone(&self) -> CefLifeSpanHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefLifeSpanHandler {
@@ -211,7 +213,8 @@ impl Clone for CefLifeSpanHandler {
 impl Drop for CefLifeSpanHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -226,7 +229,8 @@ impl CefLifeSpanHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_life_span_handler_t) -> CefLifeSpanHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefLifeSpanHandler {
@@ -240,7 +244,8 @@ impl CefLifeSpanHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_life_span_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -248,10 +253,10 @@ impl CefLifeSpanHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -280,7 +285,8 @@ impl CefLifeSpanHandler {
       client: interfaces::CefClient,
       settings: &mut interfaces::CefBrowserSettings,
       no_javascript_access: &mut libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -305,7 +311,8 @@ impl CefLifeSpanHandler {
   // Called after a new browser is created.
   //
   pub fn on_after_created(&self, browser: interfaces::CefBrowser) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -322,7 +329,8 @@ impl CefLifeSpanHandler {
   // implementation or true (1) to use a custom implementation.
   //
   pub fn run_modal(&self, browser: interfaces::CefBrowser) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -391,7 +399,8 @@ impl CefLifeSpanHandler {
   //     exist.
   //
   pub fn do_close(&self, browser: interfaces::CefBrowser) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -411,7 +420,8 @@ impl CefLifeSpanHandler {
   // additional usage information.
   //
   pub fn on_before_close(&self, browser: interfaces::CefBrowser) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -439,7 +449,8 @@ impl CefWrap<*mut cef_life_span_handler_t> for Option<CefLifeSpanHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_life_span_handler_t) -> Option<CefLifeSpanHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefLifeSpanHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_load_handler.rs b/ports/cef/interfaces/cef_load_handler.rs
index 074e07f77f1..d18a0ec3930 100644
--- a/ports/cef/interfaces/cef_load_handler.rs
+++ b/ports/cef/interfaces/cef_load_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -108,13 +109,13 @@ pub struct _cef_load_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_load_handler_t = _cef_load_handler_t;
 
@@ -131,7 +132,8 @@ pub struct CefLoadHandler {
 impl Clone for CefLoadHandler {
   fn clone(&self) -> CefLoadHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefLoadHandler {
@@ -144,7 +146,8 @@ impl Clone for CefLoadHandler {
 impl Drop for CefLoadHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -159,7 +162,8 @@ impl CefLoadHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_load_handler_t) -> CefLoadHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefLoadHandler {
@@ -173,7 +177,8 @@ impl CefLoadHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_load_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -181,10 +186,10 @@ impl CefLoadHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -196,7 +201,8 @@ impl CefLoadHandler {
   pub fn on_loading_state_change(&self, browser: interfaces::CefBrowser,
       isLoading: libc::c_int, canGoBack: libc::c_int,
       canGoForward: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -221,7 +227,8 @@ impl CefLoadHandler {
   //
   pub fn on_load_start(&self, browser: interfaces::CefBrowser,
       frame: interfaces::CefFrame) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -243,7 +250,8 @@ impl CefLoadHandler {
   //
   pub fn on_load_end(&self, browser: interfaces::CefBrowser,
       frame: interfaces::CefFrame, httpStatusCode: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -265,7 +273,8 @@ impl CefLoadHandler {
   pub fn on_load_error(&self, browser: interfaces::CefBrowser,
       frame: interfaces::CefFrame, errorCode: types::cef_errorcode_t,
       errorText: &[u16], failedUrl: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -297,7 +306,8 @@ impl CefWrap<*mut cef_load_handler_t> for Option<CefLoadHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_load_handler_t) -> Option<CefLoadHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefLoadHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_menu_model.rs b/ports/cef/interfaces/cef_menu_model.rs
index 367137e04a7..2c686f47576 100644
--- a/ports/cef/interfaces/cef_menu_model.rs
+++ b/ports/cef/interfaces/cef_menu_model.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -401,13 +402,13 @@ pub struct _cef_menu_model_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_menu_model_t = _cef_menu_model_t;
 
@@ -425,7 +426,8 @@ pub struct CefMenuModel {
 impl Clone for CefMenuModel {
   fn clone(&self) -> CefMenuModel{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefMenuModel {
@@ -438,7 +440,8 @@ impl Clone for CefMenuModel {
 impl Drop for CefMenuModel {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -453,7 +456,8 @@ impl CefMenuModel {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_menu_model_t) -> CefMenuModel {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefMenuModel {
@@ -467,7 +471,8 @@ impl CefMenuModel {
 
   pub fn c_object_addrefed(&self) -> *mut cef_menu_model_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -475,17 +480,18 @@ impl CefMenuModel {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Clears the menu. Returns true (1) on success.
   //
   pub fn clear(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -499,7 +505,8 @@ impl CefMenuModel {
   // Returns the number of items in this menu.
   //
   pub fn get_count(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -513,7 +520,8 @@ impl CefMenuModel {
   // Add a separator to the menu. Returns true (1) on success.
   //
   pub fn add_separator(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -528,7 +536,8 @@ impl CefMenuModel {
   //
   pub fn add_item(&self, command_id: libc::c_int,
       label: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -545,7 +554,8 @@ impl CefMenuModel {
   //
   pub fn add_check_item(&self, command_id: libc::c_int,
       label: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -563,7 +573,8 @@ impl CefMenuModel {
   //
   pub fn add_radio_item(&self, command_id: libc::c_int, label: &[u16],
       group_id: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -581,7 +592,8 @@ impl CefMenuModel {
   //
   pub fn add_sub_menu(&self, command_id: libc::c_int,
       label: &[u16]) -> interfaces::CefMenuModel {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -598,7 +610,8 @@ impl CefMenuModel {
   // on success.
   //
   pub fn insert_separator_at(&self, index: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -615,7 +628,8 @@ impl CefMenuModel {
   //
   pub fn insert_item_at(&self, index: libc::c_int, command_id: libc::c_int,
       label: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -634,7 +648,8 @@ impl CefMenuModel {
   //
   pub fn insert_check_item_at(&self, index: libc::c_int,
       command_id: libc::c_int, label: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -655,7 +670,8 @@ impl CefMenuModel {
   pub fn insert_radio_item_at(&self, index: libc::c_int,
       command_id: libc::c_int, label: &[u16],
       group_id: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -675,7 +691,8 @@ impl CefMenuModel {
   //
   pub fn insert_sub_menu_at(&self, index: libc::c_int, command_id: libc::c_int,
       label: &[u16]) -> interfaces::CefMenuModel {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -693,7 +710,8 @@ impl CefMenuModel {
   // success.
   //
   pub fn remove(&self, command_id: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -708,7 +726,8 @@ impl CefMenuModel {
   // Removes the item at the specified |index|. Returns true (1) on success.
   //
   pub fn remove_at(&self, index: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -724,7 +743,8 @@ impl CefMenuModel {
   // found due to the command id not existing in the menu.
   //
   pub fn get_index_of(&self, command_id: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -740,7 +760,8 @@ impl CefMenuModel {
   // invalid range or the index being a separator.
   //
   pub fn get_command_id_at(&self, index: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -756,7 +777,8 @@ impl CefMenuModel {
   //
   pub fn set_command_id_at(&self, index: libc::c_int,
       command_id: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -773,7 +795,8 @@ impl CefMenuModel {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_label(&self, command_id: libc::c_int) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -790,7 +813,8 @@ impl CefMenuModel {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_label_at(&self, index: libc::c_int) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -806,7 +830,8 @@ impl CefMenuModel {
   //
   pub fn set_label(&self, command_id: libc::c_int,
       label: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -822,7 +847,8 @@ impl CefMenuModel {
   // Set the label at the specified |index|. Returns true (1) on success.
   //
   pub fn set_label_at(&self, index: libc::c_int, label: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -839,7 +865,8 @@ impl CefMenuModel {
   //
   pub fn get_type(&self,
       command_id: libc::c_int) -> types::cef_menu_item_type_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -854,7 +881,8 @@ impl CefMenuModel {
   // Returns the item type at the specified |index|.
   //
   pub fn get_type_at(&self, index: libc::c_int) -> types::cef_menu_item_type_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -869,7 +897,8 @@ impl CefMenuModel {
   // Returns the group id for the specified |command_id| or -1 if invalid.
   //
   pub fn get_group_id(&self, command_id: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -884,7 +913,8 @@ impl CefMenuModel {
   // Returns the group id at the specified |index| or -1 if invalid.
   //
   pub fn get_group_id_at(&self, index: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -901,7 +931,8 @@ impl CefMenuModel {
   //
   pub fn set_group_id(&self, command_id: libc::c_int,
       group_id: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -918,7 +949,8 @@ impl CefMenuModel {
   //
   pub fn set_group_id_at(&self, index: libc::c_int,
       group_id: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -935,7 +967,8 @@ impl CefMenuModel {
   //
   pub fn get_sub_menu(&self,
       command_id: libc::c_int) -> interfaces::CefMenuModel {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -951,7 +984,8 @@ impl CefMenuModel {
   //
   pub fn get_sub_menu_at(&self,
       index: libc::c_int) -> interfaces::CefMenuModel {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -966,7 +1000,8 @@ impl CefMenuModel {
   // Returns true (1) if the specified |command_id| is visible.
   //
   pub fn is_visible(&self, command_id: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -981,7 +1016,8 @@ impl CefMenuModel {
   // Returns true (1) if the specified |index| is visible.
   //
   pub fn is_visible_at(&self, index: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -998,7 +1034,8 @@ impl CefMenuModel {
   //
   pub fn set_visible(&self, command_id: libc::c_int,
       visible: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1016,7 +1053,8 @@ impl CefMenuModel {
   //
   pub fn set_visible_at(&self, index: libc::c_int,
       visible: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1032,7 +1070,8 @@ impl CefMenuModel {
   // Returns true (1) if the specified |command_id| is enabled.
   //
   pub fn is_enabled(&self, command_id: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1047,7 +1086,8 @@ impl CefMenuModel {
   // Returns true (1) if the specified |index| is enabled.
   //
   pub fn is_enabled_at(&self, index: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1064,7 +1104,8 @@ impl CefMenuModel {
   //
   pub fn set_enabled(&self, command_id: libc::c_int,
       enabled: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1082,7 +1123,8 @@ impl CefMenuModel {
   //
   pub fn set_enabled_at(&self, index: libc::c_int,
       enabled: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1099,7 +1141,8 @@ impl CefMenuModel {
   // check and radio items.
   //
   pub fn is_checked(&self, command_id: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1115,7 +1158,8 @@ impl CefMenuModel {
   // and radio items.
   //
   pub fn is_checked_at(&self, index: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1132,7 +1176,8 @@ impl CefMenuModel {
   //
   pub fn set_checked(&self, command_id: libc::c_int,
       checked: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1150,7 +1195,8 @@ impl CefMenuModel {
   //
   pub fn set_checked_at(&self, index: libc::c_int,
       checked: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1167,7 +1213,8 @@ impl CefMenuModel {
   // assigned.
   //
   pub fn has_accelerator(&self, command_id: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1183,7 +1230,8 @@ impl CefMenuModel {
   // assigned.
   //
   pub fn has_accelerator_at(&self, index: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1201,7 +1249,8 @@ impl CefMenuModel {
   pub fn set_accelerator(&self, command_id: libc::c_int, key_code: libc::c_int,
       shift_pressed: libc::c_int, ctrl_pressed: libc::c_int,
       alt_pressed: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1223,7 +1272,8 @@ impl CefMenuModel {
   pub fn set_accelerator_at(&self, index: libc::c_int, key_code: libc::c_int,
       shift_pressed: libc::c_int, ctrl_pressed: libc::c_int,
       alt_pressed: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1243,7 +1293,8 @@ impl CefMenuModel {
   // true (1) on success.
   //
   pub fn remove_accelerator(&self, command_id: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1259,7 +1310,8 @@ impl CefMenuModel {
   // on success.
   //
   pub fn remove_accelerator_at(&self, index: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1278,7 +1330,8 @@ impl CefMenuModel {
       key_code: &mut libc::c_int, shift_pressed: &mut libc::c_int,
       ctrl_pressed: &mut libc::c_int,
       alt_pressed: &mut libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1301,7 +1354,8 @@ impl CefMenuModel {
       key_code: &mut libc::c_int, shift_pressed: &mut libc::c_int,
       ctrl_pressed: &mut libc::c_int,
       alt_pressed: &mut libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1333,7 +1387,8 @@ impl CefWrap<*mut cef_menu_model_t> for Option<CefMenuModel> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_menu_model_t) -> Option<CefMenuModel> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefMenuModel::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_navigation_entry.rs b/ports/cef/interfaces/cef_navigation_entry.rs
index 464f6139b29..6654b72cccb 100644
--- a/ports/cef/interfaces/cef_navigation_entry.rs
+++ b/ports/cef/interfaces/cef_navigation_entry.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -131,13 +132,13 @@ pub struct _cef_navigation_entry_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_navigation_entry_t = _cef_navigation_entry_t;
 
@@ -152,7 +153,8 @@ pub struct CefNavigationEntry {
 impl Clone for CefNavigationEntry {
   fn clone(&self) -> CefNavigationEntry{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefNavigationEntry {
@@ -165,7 +167,8 @@ impl Clone for CefNavigationEntry {
 impl Drop for CefNavigationEntry {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -180,7 +183,8 @@ impl CefNavigationEntry {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_navigation_entry_t) -> CefNavigationEntry {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefNavigationEntry {
@@ -194,7 +198,8 @@ impl CefNavigationEntry {
 
   pub fn c_object_addrefed(&self) -> *mut cef_navigation_entry_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -202,10 +207,10 @@ impl CefNavigationEntry {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -213,7 +218,8 @@ impl CefNavigationEntry {
   // if this function returns false (0).
   //
   pub fn is_valid(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -229,7 +235,8 @@ impl CefNavigationEntry {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_url(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -244,7 +251,8 @@ impl CefNavigationEntry {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_display_url(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -259,7 +267,8 @@ impl CefNavigationEntry {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_original_url(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -274,7 +283,8 @@ impl CefNavigationEntry {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_title(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -289,7 +299,8 @@ impl CefNavigationEntry {
   // this page from the previous page.
   //
   pub fn get_transition_type(&self) -> types::cef_transition_type_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -303,7 +314,8 @@ impl CefNavigationEntry {
   // Returns true (1) if this navigation includes post data.
   //
   pub fn has_post_data(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -319,7 +331,8 @@ impl CefNavigationEntry {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_frame_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -335,7 +348,8 @@ impl CefNavigationEntry {
   // 0 if the navigation has not yet completed.
   //
   pub fn get_completion_time(&self) -> types::cef_time_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -351,7 +365,8 @@ impl CefNavigationEntry {
   // navigation has not yet completed.
   //
   pub fn get_http_status_code(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -378,7 +393,8 @@ impl CefWrap<*mut cef_navigation_entry_t> for Option<CefNavigationEntry> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_navigation_entry_t) -> Option<CefNavigationEntry> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefNavigationEntry::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_origin_whitelist.rs b/ports/cef/interfaces/cef_origin_whitelist.rs
index 061f2797a3e..c396bf66e02 100644
--- a/ports/cef/interfaces/cef_origin_whitelist.rs
+++ b/ports/cef/interfaces/cef_origin_whitelist.rs
@@ -43,4 +43,5 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
diff --git a/ports/cef/interfaces/cef_parser.rs b/ports/cef/interfaces/cef_parser.rs
index 061f2797a3e..c396bf66e02 100644
--- a/ports/cef/interfaces/cef_parser.rs
+++ b/ports/cef/interfaces/cef_parser.rs
@@ -43,4 +43,5 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
diff --git a/ports/cef/interfaces/cef_path_util.rs b/ports/cef/interfaces/cef_path_util.rs
index 061f2797a3e..c396bf66e02 100644
--- a/ports/cef/interfaces/cef_path_util.rs
+++ b/ports/cef/interfaces/cef_path_util.rs
@@ -43,4 +43,5 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
diff --git a/ports/cef/interfaces/cef_print_handler.rs b/ports/cef/interfaces/cef_print_handler.rs
index c00717c88e0..9737d87a9a3 100644
--- a/ports/cef/interfaces/cef_print_handler.rs
+++ b/ports/cef/interfaces/cef_print_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -70,13 +71,13 @@ pub struct _cef_print_dialog_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_print_dialog_callback_t = _cef_print_dialog_callback_t;
 
@@ -91,7 +92,8 @@ pub struct CefPrintDialogCallback {
 impl Clone for CefPrintDialogCallback {
   fn clone(&self) -> CefPrintDialogCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefPrintDialogCallback {
@@ -104,7 +106,8 @@ impl Clone for CefPrintDialogCallback {
 impl Drop for CefPrintDialogCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -119,7 +122,8 @@ impl CefPrintDialogCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_print_dialog_callback_t) -> CefPrintDialogCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefPrintDialogCallback {
@@ -133,7 +137,8 @@ impl CefPrintDialogCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_print_dialog_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -141,17 +146,18 @@ impl CefPrintDialogCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Continue printing with the specified |settings|.
   //
   pub fn cont(&self, settings: interfaces::CefPrintSettings) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -166,7 +172,8 @@ impl CefPrintDialogCallback {
   // Cancel the printing.
   //
   pub fn cancel(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -193,7 +200,8 @@ impl CefWrap<*mut cef_print_dialog_callback_t> for Option<CefPrintDialogCallback
     }
   }
   unsafe fn to_rust(c_object: *mut cef_print_dialog_callback_t) -> Option<CefPrintDialogCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefPrintDialogCallback::from_c_object_addref(c_object))
@@ -220,13 +228,13 @@ pub struct _cef_print_job_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_print_job_callback_t = _cef_print_job_callback_t;
 
@@ -241,7 +249,8 @@ pub struct CefPrintJobCallback {
 impl Clone for CefPrintJobCallback {
   fn clone(&self) -> CefPrintJobCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefPrintJobCallback {
@@ -254,7 +263,8 @@ impl Clone for CefPrintJobCallback {
 impl Drop for CefPrintJobCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -269,7 +279,8 @@ impl CefPrintJobCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_print_job_callback_t) -> CefPrintJobCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefPrintJobCallback {
@@ -283,7 +294,8 @@ impl CefPrintJobCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_print_job_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -291,17 +303,18 @@ impl CefPrintJobCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Indicate completion of the print job.
   //
   pub fn cont(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -328,7 +341,8 @@ impl CefWrap<*mut cef_print_job_callback_t> for Option<CefPrintJobCallback> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_print_job_callback_t) -> Option<CefPrintJobCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefPrintJobCallback::from_c_object_addref(c_object))
@@ -385,13 +399,13 @@ pub struct _cef_print_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_print_handler_t = _cef_print_handler_t;
 
@@ -407,7 +421,8 @@ pub struct CefPrintHandler {
 impl Clone for CefPrintHandler {
   fn clone(&self) -> CefPrintHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefPrintHandler {
@@ -420,7 +435,8 @@ impl Clone for CefPrintHandler {
 impl Drop for CefPrintHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -435,7 +451,8 @@ impl CefPrintHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_print_handler_t) -> CefPrintHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefPrintHandler {
@@ -449,7 +466,8 @@ impl CefPrintHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_print_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -457,10 +475,10 @@ impl CefPrintHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -470,7 +488,8 @@ impl CefPrintHandler {
   //
   pub fn on_print_settings(&self, settings: interfaces::CefPrintSettings,
       get_defaults: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -489,7 +508,8 @@ impl CefPrintHandler {
   //
   pub fn on_print_dialog(&self, has_selection: libc::c_int,
       callback: interfaces::CefPrintDialogCallback) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -508,7 +528,8 @@ impl CefPrintHandler {
   //
   pub fn on_print_job(&self, document_name: &[u16], pdf_file_path: &[u16],
       callback: interfaces::CefPrintJobCallback) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -525,7 +546,8 @@ impl CefPrintHandler {
   // Reset client state related to printing.
   //
   pub fn on_print_reset(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -552,7 +574,8 @@ impl CefWrap<*mut cef_print_handler_t> for Option<CefPrintHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_print_handler_t) -> Option<CefPrintHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefPrintHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_print_settings.rs b/ports/cef/interfaces/cef_print_settings.rs
index 6af6381f506..2c22df782ad 100644
--- a/ports/cef/interfaces/cef_print_settings.rs
+++ b/ports/cef/interfaces/cef_print_settings.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -206,13 +207,13 @@ pub struct _cef_print_settings_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_print_settings_t = _cef_print_settings_t;
 
@@ -227,7 +228,8 @@ pub struct CefPrintSettings {
 impl Clone for CefPrintSettings {
   fn clone(&self) -> CefPrintSettings{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefPrintSettings {
@@ -240,7 +242,8 @@ impl Clone for CefPrintSettings {
 impl Drop for CefPrintSettings {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -255,7 +258,8 @@ impl CefPrintSettings {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_print_settings_t) -> CefPrintSettings {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefPrintSettings {
@@ -269,7 +273,8 @@ impl CefPrintSettings {
 
   pub fn c_object_addrefed(&self) -> *mut cef_print_settings_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -277,10 +282,10 @@ impl CefPrintSettings {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -288,7 +293,8 @@ impl CefPrintSettings {
   // if this function returns false (0).
   //
   pub fn is_valid(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -303,7 +309,8 @@ impl CefPrintSettings {
   // expose read-only objects.
   //
   pub fn is_read_only(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -317,7 +324,8 @@ impl CefPrintSettings {
   // Returns a writable copy of this object.
   //
   pub fn copy(&self) -> interfaces::CefPrintSettings {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -331,7 +339,8 @@ impl CefPrintSettings {
   // Set the page orientation.
   //
   pub fn set_orientation(&self, landscape: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -346,7 +355,8 @@ impl CefPrintSettings {
   // Returns true (1) if the orientation is landscape.
   //
   pub fn is_landscape(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -365,7 +375,8 @@ impl CefPrintSettings {
       physical_size_device_units: &types::cef_size_t,
       printable_area_device_units: &types::cef_rect_t,
       landscape_needs_flip: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -382,7 +393,8 @@ impl CefPrintSettings {
   // Set the device name.
   //
   pub fn set_device_name(&self, name: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -398,7 +410,8 @@ impl CefPrintSettings {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_device_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -412,7 +425,8 @@ impl CefPrintSettings {
   // Set the DPI (dots per inch).
   //
   pub fn set_dpi(&self, dpi: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -427,7 +441,8 @@ impl CefPrintSettings {
   // Get the DPI (dots per inch).
   //
   pub fn get_dpi(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -442,7 +457,8 @@ impl CefPrintSettings {
   //
   pub fn set_page_ranges(&self, ranges_count: libc::size_t,
       ranges: *const types::cef_page_range_t) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -458,7 +474,8 @@ impl CefPrintSettings {
   // Returns the number of page ranges that currently exist.
   //
   pub fn get_page_ranges_count(&self) -> libc::size_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -473,7 +490,8 @@ impl CefPrintSettings {
   //
   pub fn get_page_ranges(&self, ranges_count: *mut libc::size_t,
       ranges: *mut types::cef_page_range_t) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -489,7 +507,8 @@ impl CefPrintSettings {
   // Set whether only the selection will be printed.
   //
   pub fn set_selection_only(&self, selection_only: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -504,7 +523,8 @@ impl CefPrintSettings {
   // Returns true (1) if only the selection will be printed.
   //
   pub fn is_selection_only(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -518,7 +538,8 @@ impl CefPrintSettings {
   // Set whether pages will be collated.
   //
   pub fn set_collate(&self, collate: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -533,7 +554,8 @@ impl CefPrintSettings {
   // Returns true (1) if pages will be collated.
   //
   pub fn will_collate(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -547,7 +569,8 @@ impl CefPrintSettings {
   // Set the color model.
   //
   pub fn set_color_model(&self, model: types::cef_color_model_t) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -562,7 +585,8 @@ impl CefPrintSettings {
   // Get the color model.
   //
   pub fn get_color_model(&self) -> types::cef_color_model_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -576,7 +600,8 @@ impl CefPrintSettings {
   // Set the number of copies.
   //
   pub fn set_copies(&self, copies: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -591,7 +616,8 @@ impl CefPrintSettings {
   // Get the number of copies.
   //
   pub fn get_copies(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -605,7 +631,8 @@ impl CefPrintSettings {
   // Set the duplex mode.
   //
   pub fn set_duplex_mode(&self, mode: types::cef_duplex_mode_t) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -620,7 +647,8 @@ impl CefPrintSettings {
   // Get the duplex mode.
   //
   pub fn get_duplex_mode(&self) -> types::cef_duplex_mode_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -658,7 +686,8 @@ impl CefWrap<*mut cef_print_settings_t> for Option<CefPrintSettings> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_print_settings_t) -> Option<CefPrintSettings> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefPrintSettings::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_process_message.rs b/ports/cef/interfaces/cef_process_message.rs
index da6e840e78c..e09b4b1ee15 100644
--- a/ports/cef/interfaces/cef_process_message.rs
+++ b/ports/cef/interfaces/cef_process_message.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -91,13 +92,13 @@ pub struct _cef_process_message_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_process_message_t = _cef_process_message_t;
 
@@ -112,7 +113,8 @@ pub struct CefProcessMessage {
 impl Clone for CefProcessMessage {
   fn clone(&self) -> CefProcessMessage{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefProcessMessage {
@@ -125,7 +127,8 @@ impl Clone for CefProcessMessage {
 impl Drop for CefProcessMessage {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -140,7 +143,8 @@ impl CefProcessMessage {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_process_message_t) -> CefProcessMessage {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefProcessMessage {
@@ -154,7 +158,8 @@ impl CefProcessMessage {
 
   pub fn c_object_addrefed(&self) -> *mut cef_process_message_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -162,10 +167,10 @@ impl CefProcessMessage {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -173,7 +178,8 @@ impl CefProcessMessage {
   // if this function returns false (0).
   //
   pub fn is_valid(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -188,7 +194,8 @@ impl CefProcessMessage {
   // expose read-only objects.
   //
   pub fn is_read_only(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -202,7 +209,8 @@ impl CefProcessMessage {
   // Returns a writable copy of this object.
   //
   pub fn copy(&self) -> interfaces::CefProcessMessage {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -217,7 +225,8 @@ impl CefProcessMessage {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -231,7 +240,8 @@ impl CefProcessMessage {
   // Returns the list of arguments.
   //
   pub fn get_argument_list(&self) -> interfaces::CefListValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -269,7 +279,8 @@ impl CefWrap<*mut cef_process_message_t> for Option<CefProcessMessage> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_process_message_t) -> Option<CefProcessMessage> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefProcessMessage::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_process_util.rs b/ports/cef/interfaces/cef_process_util.rs
index 061f2797a3e..c396bf66e02 100644
--- a/ports/cef/interfaces/cef_process_util.rs
+++ b/ports/cef/interfaces/cef_process_util.rs
@@ -43,4 +43,5 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
diff --git a/ports/cef/interfaces/cef_render_handler.rs b/ports/cef/interfaces/cef_render_handler.rs
index 384a2b14b40..68beac427ab 100644
--- a/ports/cef/interfaces/cef_render_handler.rs
+++ b/ports/cef/interfaces/cef_render_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -190,13 +191,13 @@ pub struct _cef_render_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_render_handler_t = _cef_render_handler_t;
 
@@ -212,7 +213,8 @@ pub struct CefRenderHandler {
 impl Clone for CefRenderHandler {
   fn clone(&self) -> CefRenderHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefRenderHandler {
@@ -225,7 +227,8 @@ impl Clone for CefRenderHandler {
 impl Drop for CefRenderHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -240,7 +243,8 @@ impl CefRenderHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_render_handler_t) -> CefRenderHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefRenderHandler {
@@ -254,7 +258,8 @@ impl CefRenderHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_render_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -262,10 +267,10 @@ impl CefRenderHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -274,7 +279,8 @@ impl CefRenderHandler {
   //
   pub fn get_root_screen_rect(&self, browser: interfaces::CefBrowser,
       rect: &mut types::cef_rect_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -292,7 +298,8 @@ impl CefRenderHandler {
   //
   pub fn get_view_rect(&self, browser: interfaces::CefBrowser,
       rect: &mut types::cef_rect_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -311,7 +318,8 @@ impl CefRenderHandler {
   pub fn get_screen_point(&self, browser: interfaces::CefBrowser,
       viewX: libc::c_int, viewY: libc::c_int, screenX: &mut libc::c_int,
       screenY: &mut libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -337,7 +345,8 @@ impl CefRenderHandler {
   //
   pub fn get_screen_info(&self, browser: interfaces::CefBrowser,
       screen_info: &mut interfaces::CefScreenInfo) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -355,7 +364,8 @@ impl CefRenderHandler {
   //
   pub fn on_popup_show(&self, browser: interfaces::CefBrowser,
       show: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -373,7 +383,8 @@ impl CefRenderHandler {
   //
   pub fn on_popup_size(&self, browser: interfaces::CefBrowser,
       rect: &types::cef_rect_t) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -399,7 +410,8 @@ impl CefRenderHandler {
       ty: types::cef_paint_element_type_t, dirtyRects_count: libc::size_t,
       dirtyRects: *const types::cef_rect_t, buffer: &(), width: libc::c_int,
       height: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -423,7 +435,8 @@ impl CefRenderHandler {
   pub fn on_cursor_change(&self, browser: interfaces::CefBrowser,
       cursor: types::cef_cursor_handle_t, ty: types::cef_cursor_type_t,
       custom_cursor_info: &interfaces::CefCursorInfo) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -455,7 +468,8 @@ impl CefRenderHandler {
       drag_data: interfaces::CefDragData,
       allowed_ops: types::cef_drag_operations_mask_t, x: libc::c_int,
       y: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -477,7 +491,8 @@ impl CefRenderHandler {
   //
   pub fn update_drag_cursor(&self, browser: interfaces::CefBrowser,
       operation: types::cef_drag_operations_mask_t) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -494,7 +509,8 @@ impl CefRenderHandler {
   //
   pub fn on_scroll_offset_changed(&self, browser: interfaces::CefBrowser,
       x: libc::c_double, y: libc::c_double) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -515,7 +531,8 @@ impl CefRenderHandler {
   //
   pub fn get_backing_rect(&self, browser: interfaces::CefBrowser,
       rect: &mut types::cef_rect_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -532,7 +549,8 @@ impl CefRenderHandler {
   // flip). This is called only during accelerated compositing.
   //
   pub fn on_present(&self, browser: interfaces::CefBrowser) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -560,7 +578,8 @@ impl CefWrap<*mut cef_render_handler_t> for Option<CefRenderHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_render_handler_t) -> Option<CefRenderHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefRenderHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_render_process_handler.rs b/ports/cef/interfaces/cef_render_process_handler.rs
index 4c9bbc67dc6..c334c9520e8 100644
--- a/ports/cef/interfaces/cef_render_process_handler.rs
+++ b/ports/cef/interfaces/cef_render_process_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -173,13 +174,13 @@ pub struct _cef_render_process_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_render_process_handler_t = _cef_render_process_handler_t;
 
@@ -196,7 +197,8 @@ pub struct CefRenderProcessHandler {
 impl Clone for CefRenderProcessHandler {
   fn clone(&self) -> CefRenderProcessHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefRenderProcessHandler {
@@ -209,7 +211,8 @@ impl Clone for CefRenderProcessHandler {
 impl Drop for CefRenderProcessHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -224,7 +227,8 @@ impl CefRenderProcessHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_render_process_handler_t) -> CefRenderProcessHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefRenderProcessHandler {
@@ -238,7 +242,8 @@ impl CefRenderProcessHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_render_process_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -246,10 +251,10 @@ impl CefRenderProcessHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -260,7 +265,8 @@ impl CefRenderProcessHandler {
   //
   pub fn on_render_thread_created(&self,
       extra_info: interfaces::CefListValue) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -275,7 +281,8 @@ impl CefRenderProcessHandler {
   // Called after WebKit has been initialized.
   //
   pub fn on_web_kit_initialized(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -291,7 +298,8 @@ impl CefRenderProcessHandler {
   // destroyed.
   //
   pub fn on_browser_created(&self, browser: interfaces::CefBrowser) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -306,7 +314,8 @@ impl CefRenderProcessHandler {
   // Called before a browser is destroyed.
   //
   pub fn on_browser_destroyed(&self, browser: interfaces::CefBrowser) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -321,7 +330,8 @@ impl CefRenderProcessHandler {
   // Return the handler for browser load status events.
   //
   pub fn get_load_handler(&self) -> interfaces::CefLoadHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -340,7 +350,8 @@ impl CefRenderProcessHandler {
       frame: interfaces::CefFrame, request: interfaces::CefRequest,
       navigation_type: types::cef_navigation_type_t,
       is_redirect: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -365,7 +376,8 @@ impl CefRenderProcessHandler {
   //
   pub fn on_context_created(&self, browser: interfaces::CefBrowser,
       frame: interfaces::CefFrame, context: interfaces::CefV8Context) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -384,7 +396,8 @@ impl CefRenderProcessHandler {
   //
   pub fn on_context_released(&self, browser: interfaces::CefBrowser,
       frame: interfaces::CefFrame, context: interfaces::CefV8Context) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -406,7 +419,8 @@ impl CefRenderProcessHandler {
       frame: interfaces::CefFrame, context: interfaces::CefV8Context,
       exception: interfaces::CefV8Exception,
       stackTrace: interfaces::CefV8StackTrace) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -431,7 +445,8 @@ impl CefRenderProcessHandler {
   //
   pub fn on_focused_node_changed(&self, browser: interfaces::CefBrowser,
       frame: interfaces::CefFrame, node: interfaces::CefDOMNode) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -452,7 +467,8 @@ impl CefRenderProcessHandler {
   pub fn on_process_message_received(&self, browser: interfaces::CefBrowser,
       source_process: interfaces::CefProcessId,
       message: interfaces::CefProcessMessage) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -482,7 +498,8 @@ impl CefWrap<*mut cef_render_process_handler_t> for Option<CefRenderProcessHandl
     }
   }
   unsafe fn to_rust(c_object: *mut cef_render_process_handler_t) -> Option<CefRenderProcessHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefRenderProcessHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_request.rs b/ports/cef/interfaces/cef_request.rs
index 574f59bb3db..171d3c30314 100644
--- a/ports/cef/interfaces/cef_request.rs
+++ b/ports/cef/interfaces/cef_request.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -174,13 +175,13 @@ pub struct _cef_request_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_request_t = _cef_request_t;
 
@@ -196,7 +197,8 @@ pub struct CefRequest {
 impl Clone for CefRequest {
   fn clone(&self) -> CefRequest{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefRequest {
@@ -209,7 +211,8 @@ impl Clone for CefRequest {
 impl Drop for CefRequest {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -224,7 +227,8 @@ impl CefRequest {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_request_t) -> CefRequest {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefRequest {
@@ -238,7 +242,8 @@ impl CefRequest {
 
   pub fn c_object_addrefed(&self) -> *mut cef_request_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -246,17 +251,18 @@ impl CefRequest {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Returns true (1) if this object is read-only.
   //
   pub fn is_read_only(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -271,7 +277,8 @@ impl CefRequest {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_url(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -285,7 +292,8 @@ impl CefRequest {
   // Set the fully qualified URL.
   //
   pub fn set_url(&self, url: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -302,7 +310,8 @@ impl CefRequest {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_method(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -316,7 +325,8 @@ impl CefRequest {
   // Set the request function type.
   //
   pub fn set_method(&self, method: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -331,7 +341,8 @@ impl CefRequest {
   // Get the post data.
   //
   pub fn get_post_data(&self) -> interfaces::CefPostData {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -345,7 +356,8 @@ impl CefRequest {
   // Set the post data.
   //
   pub fn set_post_data(&self, postData: interfaces::CefPostData) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -360,7 +372,8 @@ impl CefRequest {
   // Get the header values.
   //
   pub fn get_header_map(&self, headerMap: HashMap<String,Vec<String>>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -375,7 +388,8 @@ impl CefRequest {
   // Set the header values.
   //
   pub fn set_header_map(&self, headerMap: HashMap<String,Vec<String>>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -392,7 +406,8 @@ impl CefRequest {
   pub fn set(&self, url: &[u16], method: &[u16],
       postData: interfaces::CefPostData, headerMap: HashMap<String,
       Vec<String>>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -411,7 +426,8 @@ impl CefRequest {
   // cef_urlrequest_flags_t for supported values.
   //
   pub fn get_flags(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -426,7 +442,8 @@ impl CefRequest {
   // cef_urlrequest_flags_t for supported values.
   //
   pub fn set_flags(&self, flags: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -443,7 +460,8 @@ impl CefRequest {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_first_party_for_cookies(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -458,7 +476,8 @@ impl CefRequest {
   // cef_urlrequest_t.
   //
   pub fn set_first_party_for_cookies(&self, url: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -474,7 +493,8 @@ impl CefRequest {
   // process.
   //
   pub fn get_resource_type(&self) -> types::cef_resource_type_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -490,7 +510,8 @@ impl CefRequest {
   // frame navigation.
   //
   pub fn get_transition_type(&self) -> types::cef_transition_type_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -506,7 +527,8 @@ impl CefRequest {
   // browser process to track a single request across multiple callbacks.
   //
   pub fn get_identifier(&self) -> u64 {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -544,7 +566,8 @@ impl CefWrap<*mut cef_request_t> for Option<CefRequest> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_request_t) -> Option<CefRequest> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefRequest::from_c_object_addref(c_object))
@@ -604,13 +627,13 @@ pub struct _cef_post_data_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_post_data_t = _cef_post_data_t;
 
@@ -626,7 +649,8 @@ pub struct CefPostData {
 impl Clone for CefPostData {
   fn clone(&self) -> CefPostData{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefPostData {
@@ -639,7 +663,8 @@ impl Clone for CefPostData {
 impl Drop for CefPostData {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -654,7 +679,8 @@ impl CefPostData {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_post_data_t) -> CefPostData {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefPostData {
@@ -668,7 +694,8 @@ impl CefPostData {
 
   pub fn c_object_addrefed(&self) -> *mut cef_post_data_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -676,17 +703,18 @@ impl CefPostData {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Returns true (1) if this object is read-only.
   //
   pub fn is_read_only(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -700,7 +728,8 @@ impl CefPostData {
   // Returns the number of existing post data elements.
   //
   pub fn get_element_count(&self) -> libc::size_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -715,7 +744,8 @@ impl CefPostData {
   //
   pub fn get_elements(&self, elements_count: *mut libc::size_t,
       elements: *mut interfaces::CefPostDataElement) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -733,7 +763,8 @@ impl CefPostData {
   //
   pub fn remove_element(&self,
       element: interfaces::CefPostDataElement) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -749,7 +780,8 @@ impl CefPostData {
   //
   pub fn add_element(&self,
       element: interfaces::CefPostDataElement) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -764,7 +796,8 @@ impl CefPostData {
   // Remove all existing post data elements.
   //
   pub fn remove_elements(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -802,7 +835,8 @@ impl CefWrap<*mut cef_post_data_t> for Option<CefPostData> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_post_data_t) -> Option<CefPostData> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefPostData::from_c_object_addref(c_object))
@@ -876,13 +910,13 @@ pub struct _cef_post_data_element_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_post_data_element_t = _cef_post_data_element_t;
 
@@ -898,7 +932,8 @@ pub struct CefPostDataElement {
 impl Clone for CefPostDataElement {
   fn clone(&self) -> CefPostDataElement{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefPostDataElement {
@@ -911,7 +946,8 @@ impl Clone for CefPostDataElement {
 impl Drop for CefPostDataElement {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -926,7 +962,8 @@ impl CefPostDataElement {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_post_data_element_t) -> CefPostDataElement {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefPostDataElement {
@@ -940,7 +977,8 @@ impl CefPostDataElement {
 
   pub fn c_object_addrefed(&self) -> *mut cef_post_data_element_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -948,17 +986,18 @@ impl CefPostDataElement {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Returns true (1) if this object is read-only.
   //
   pub fn is_read_only(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -972,7 +1011,8 @@ impl CefPostDataElement {
   // Remove all contents from the post data element.
   //
   pub fn set_to_empty(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -986,7 +1026,8 @@ impl CefPostDataElement {
   // The post data element will represent a file.
   //
   pub fn set_to_file(&self, fileName: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1002,7 +1043,8 @@ impl CefPostDataElement {
   // copied.
   //
   pub fn set_to_bytes(&self, size: libc::size_t, bytes: &()) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1018,7 +1060,8 @@ impl CefPostDataElement {
   // Return the type of this post data element.
   //
   pub fn get_type(&self) -> types::cef_postdataelement_type_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1033,7 +1076,8 @@ impl CefPostDataElement {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_file(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1047,7 +1091,8 @@ impl CefPostDataElement {
   // Return the number of bytes.
   //
   pub fn get_bytes_count(&self) -> libc::size_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1062,7 +1107,8 @@ impl CefPostDataElement {
   // actually read.
   //
   pub fn get_bytes(&self, size: libc::size_t, bytes: &mut ()) -> libc::size_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1102,7 +1148,8 @@ impl CefWrap<*mut cef_post_data_element_t> for Option<CefPostDataElement> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_post_data_element_t) -> Option<CefPostDataElement> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefPostDataElement::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_request_context.rs b/ports/cef/interfaces/cef_request_context.rs
index 29bfa3a52c0..7f4f4fc975b 100644
--- a/ports/cef/interfaces/cef_request_context.rs
+++ b/ports/cef/interfaces/cef_request_context.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -144,13 +145,13 @@ pub struct _cef_request_context_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_request_context_t = _cef_request_context_t;
 
@@ -178,7 +179,8 @@ pub struct CefRequestContext {
 impl Clone for CefRequestContext {
   fn clone(&self) -> CefRequestContext{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefRequestContext {
@@ -191,7 +193,8 @@ impl Clone for CefRequestContext {
 impl Drop for CefRequestContext {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -206,7 +209,8 @@ impl CefRequestContext {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_request_context_t) -> CefRequestContext {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefRequestContext {
@@ -220,7 +224,8 @@ impl CefRequestContext {
 
   pub fn c_object_addrefed(&self) -> *mut cef_request_context_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -228,10 +233,10 @@ impl CefRequestContext {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -239,7 +244,8 @@ impl CefRequestContext {
   // object.
   //
   pub fn is_same(&self, other: interfaces::CefRequestContext) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -256,7 +262,8 @@ impl CefRequestContext {
   //
   pub fn is_sharing_with(&self,
       other: interfaces::CefRequestContext) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -273,7 +280,8 @@ impl CefRequestContext {
   // context argument.
   //
   pub fn is_global(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -287,7 +295,8 @@ impl CefRequestContext {
   // Returns the handler for this context if any.
   //
   pub fn get_handler(&self) -> interfaces::CefRequestContextHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -303,7 +312,8 @@ impl CefRequestContext {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_cache_path(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -323,7 +333,8 @@ impl CefRequestContext {
   //
   pub fn get_default_cookie_manager(&self,
       callback: interfaces::CefCompletionCallback) -> interfaces::CefCookieManager {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -350,7 +361,8 @@ impl CefRequestContext {
   pub fn register_scheme_handler_factory(&self, scheme_name: &[u16],
       domain_name: &[u16],
       factory: interfaces::CefSchemeHandlerFactory) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -368,7 +380,8 @@ impl CefRequestContext {
   // This function may be called on any thread in the browser process.
   //
   pub fn clear_scheme_handler_factories(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -434,7 +447,8 @@ impl CefWrap<*mut cef_request_context_t> for Option<CefRequestContext> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_request_context_t) -> Option<CefRequestContext> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefRequestContext::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_request_context_handler.rs b/ports/cef/interfaces/cef_request_context_handler.rs
index 30a325bfe9d..91e41a1b91e 100644
--- a/ports/cef/interfaces/cef_request_context_handler.rs
+++ b/ports/cef/interfaces/cef_request_context_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -68,13 +69,13 @@ pub struct _cef_request_context_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_request_context_handler_t = _cef_request_context_handler_t;
 
@@ -91,7 +92,8 @@ pub struct CefRequestContextHandler {
 impl Clone for CefRequestContextHandler {
   fn clone(&self) -> CefRequestContextHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefRequestContextHandler {
@@ -104,7 +106,8 @@ impl Clone for CefRequestContextHandler {
 impl Drop for CefRequestContextHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -119,7 +122,8 @@ impl CefRequestContextHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_request_context_handler_t) -> CefRequestContextHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefRequestContextHandler {
@@ -133,7 +137,8 @@ impl CefRequestContextHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_request_context_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -141,10 +146,10 @@ impl CefRequestContextHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -153,7 +158,8 @@ impl CefRequestContextHandler {
   // cef_request_tContext::get_default_cookie_manager() will be used.
   //
   pub fn get_cookie_manager(&self) -> interfaces::CefCookieManager {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -180,7 +186,8 @@ impl CefWrap<*mut cef_request_context_handler_t> for Option<CefRequestContextHan
     }
   }
   unsafe fn to_rust(c_object: *mut cef_request_context_handler_t) -> Option<CefRequestContextHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefRequestContextHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_request_handler.rs b/ports/cef/interfaces/cef_request_handler.rs
index c17a9015181..483d26adb9b 100644
--- a/ports/cef/interfaces/cef_request_handler.rs
+++ b/ports/cef/interfaces/cef_request_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -70,13 +71,13 @@ pub struct _cef_request_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_request_callback_t = _cef_request_callback_t;
 
@@ -91,7 +92,8 @@ pub struct CefRequestCallback {
 impl Clone for CefRequestCallback {
   fn clone(&self) -> CefRequestCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefRequestCallback {
@@ -104,7 +106,8 @@ impl Clone for CefRequestCallback {
 impl Drop for CefRequestCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -119,7 +122,8 @@ impl CefRequestCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_request_callback_t) -> CefRequestCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefRequestCallback {
@@ -133,7 +137,8 @@ impl CefRequestCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_request_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -141,10 +146,10 @@ impl CefRequestCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -152,7 +157,8 @@ impl CefRequestCallback {
   // continued. Otherwise, the request will be canceled.
   //
   pub fn cont(&self, allow: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -167,7 +173,8 @@ impl CefRequestCallback {
   // Cancel the url request.
   //
   pub fn cancel(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -194,7 +201,8 @@ impl CefWrap<*mut cef_request_callback_t> for Option<CefRequestCallback> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_request_callback_t) -> Option<CefRequestCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefRequestCallback::from_c_object_addref(c_object))
@@ -396,13 +404,13 @@ pub struct _cef_request_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_request_handler_t = _cef_request_handler_t;
 
@@ -418,7 +426,8 @@ pub struct CefRequestHandler {
 impl Clone for CefRequestHandler {
   fn clone(&self) -> CefRequestHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefRequestHandler {
@@ -431,7 +440,8 @@ impl Clone for CefRequestHandler {
 impl Drop for CefRequestHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -446,7 +456,8 @@ impl CefRequestHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_request_handler_t) -> CefRequestHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefRequestHandler {
@@ -460,7 +471,8 @@ impl CefRequestHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_request_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -468,10 +480,10 @@ impl CefRequestHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -487,7 +499,8 @@ impl CefRequestHandler {
   pub fn on_before_browse(&self, browser: interfaces::CefBrowser,
       frame: interfaces::CefFrame, request: interfaces::CefRequest,
       is_redirect: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -521,7 +534,8 @@ impl CefRequestHandler {
       frame: interfaces::CefFrame, target_url: &[u16],
       target_disposition: types::cef_window_open_disposition_t,
       user_gesture: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -547,7 +561,8 @@ impl CefRequestHandler {
   pub fn on_before_resource_load(&self, browser: interfaces::CefBrowser,
       frame: interfaces::CefFrame, request: interfaces::CefRequest,
       callback: interfaces::CefRequestCallback) -> types::cef_return_value_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -570,7 +585,8 @@ impl CefRequestHandler {
   pub fn get_resource_handler(&self, browser: interfaces::CefBrowser,
       frame: interfaces::CefFrame,
       request: interfaces::CefRequest) -> interfaces::CefResourceHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -592,7 +608,8 @@ impl CefRequestHandler {
   pub fn on_resource_redirect(&self, browser: interfaces::CefBrowser,
       frame: interfaces::CefFrame, request: interfaces::CefRequest,
       new_url: *mut types::cef_string_t) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -615,7 +632,8 @@ impl CefRequestHandler {
   pub fn on_resource_response(&self, browser: interfaces::CefBrowser,
       frame: interfaces::CefFrame, request: interfaces::CefRequest,
       response: interfaces::CefResponse) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -641,7 +659,8 @@ impl CefRequestHandler {
       frame: interfaces::CefFrame, isProxy: libc::c_int, host: &[u16],
       port: libc::c_int, realm: &[u16], scheme: &[u16],
       callback: interfaces::CefAuthCallback) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -671,7 +690,8 @@ impl CefRequestHandler {
   pub fn on_quota_request(&self, browser: interfaces::CefBrowser,
       origin_url: &[u16], new_size: i64,
       callback: interfaces::CefRequestCallback) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -694,7 +714,8 @@ impl CefRequestHandler {
   //
   pub fn on_protocol_execution(&self, browser: interfaces::CefBrowser,
       url: &[u16], allow_os_execution: &mut libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -720,7 +741,8 @@ impl CefRequestHandler {
       cert_error: types::cef_errorcode_t, request_url: &[u16],
       ssl_info: interfaces::CefSSLInfo,
       callback: interfaces::CefRequestCallback) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -742,7 +764,8 @@ impl CefRequestHandler {
   pub fn on_before_plugin_load(&self, browser: interfaces::CefBrowser,
       url: &[u16], policy_url: &[u16],
       info: interfaces::CefWebPluginInfo) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -762,7 +785,8 @@ impl CefRequestHandler {
   //
   pub fn on_plugin_crashed(&self, browser: interfaces::CefBrowser,
       plugin_path: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -780,7 +804,8 @@ impl CefRequestHandler {
   // process.
   //
   pub fn on_render_view_ready(&self, browser: interfaces::CefBrowser) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -797,7 +822,8 @@ impl CefRequestHandler {
   //
   pub fn on_render_process_terminated(&self, browser: interfaces::CefBrowser,
       status: types::cef_termination_status_t) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -826,7 +852,8 @@ impl CefWrap<*mut cef_request_handler_t> for Option<CefRequestHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_request_handler_t) -> Option<CefRequestHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefRequestHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_resource_bundle_handler.rs b/ports/cef/interfaces/cef_resource_bundle_handler.rs
index a99c1946d9e..d6501c0ea56 100644
--- a/ports/cef/interfaces/cef_resource_bundle_handler.rs
+++ b/ports/cef/interfaces/cef_resource_bundle_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -82,13 +83,13 @@ pub struct _cef_resource_bundle_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_resource_bundle_handler_t = _cef_resource_bundle_handler_t;
 
@@ -104,7 +105,8 @@ pub struct CefResourceBundleHandler {
 impl Clone for CefResourceBundleHandler {
   fn clone(&self) -> CefResourceBundleHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefResourceBundleHandler {
@@ -117,7 +119,8 @@ impl Clone for CefResourceBundleHandler {
 impl Drop for CefResourceBundleHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -132,7 +135,8 @@ impl CefResourceBundleHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_resource_bundle_handler_t) -> CefResourceBundleHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefResourceBundleHandler {
@@ -146,7 +150,8 @@ impl CefResourceBundleHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_resource_bundle_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -154,10 +159,10 @@ impl CefResourceBundleHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -168,7 +173,8 @@ impl CefResourceBundleHandler {
   //
   pub fn get_localized_string(&self, message_id: libc::c_int,
       string: *mut types::cef_string_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -191,7 +197,8 @@ impl CefResourceBundleHandler {
   pub fn get_data_resource(&self, resource_id: libc::c_int,
       data: &mut *mut libc::c_void,
       data_size: &mut libc::size_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -221,7 +228,8 @@ impl CefWrap<*mut cef_resource_bundle_handler_t> for Option<CefResourceBundleHan
     }
   }
   unsafe fn to_rust(c_object: *mut cef_resource_bundle_handler_t) -> Option<CefResourceBundleHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefResourceBundleHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_resource_handler.rs b/ports/cef/interfaces/cef_resource_handler.rs
index a374210b591..a6ecd42bc2e 100644
--- a/ports/cef/interfaces/cef_resource_handler.rs
+++ b/ports/cef/interfaces/cef_resource_handler.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -117,13 +118,13 @@ pub struct _cef_resource_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_resource_handler_t = _cef_resource_handler_t;
 
@@ -139,7 +140,8 @@ pub struct CefResourceHandler {
 impl Clone for CefResourceHandler {
   fn clone(&self) -> CefResourceHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefResourceHandler {
@@ -152,7 +154,8 @@ impl Clone for CefResourceHandler {
 impl Drop for CefResourceHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -167,7 +170,8 @@ impl CefResourceHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_resource_handler_t) -> CefResourceHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefResourceHandler {
@@ -181,7 +185,8 @@ impl CefResourceHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_resource_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -189,10 +194,10 @@ impl CefResourceHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -204,7 +209,8 @@ impl CefResourceHandler {
   //
   pub fn process_request(&self, request: interfaces::CefRequest,
       callback: interfaces::CefCallback) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -229,7 +235,8 @@ impl CefResourceHandler {
   pub fn get_response_headers(&self, response: interfaces::CefResponse,
       response_length: &mut i64, redirectUrl: *mut types::cef_string_t) -> (
       ) {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -252,7 +259,8 @@ impl CefResourceHandler {
   pub fn read_response(&self, data_out: &mut (), bytes_to_read: libc::c_int,
       bytes_read: &mut libc::c_int,
       callback: interfaces::CefCallback) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -272,7 +280,8 @@ impl CefResourceHandler {
   // cookies will be sent with the request.
   //
   pub fn can_get_cookie(&self, cookie: &interfaces::CefCookie) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -288,7 +297,8 @@ impl CefResourceHandler {
   // set or false (0) otherwise.
   //
   pub fn can_set_cookie(&self, cookie: &interfaces::CefCookie) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -303,7 +313,8 @@ impl CefResourceHandler {
   // Request processing has been canceled.
   //
   pub fn cancel(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -330,7 +341,8 @@ impl CefWrap<*mut cef_resource_handler_t> for Option<CefResourceHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_resource_handler_t) -> Option<CefResourceHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefResourceHandler::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_response.rs b/ports/cef/interfaces/cef_response.rs
index 6c97d22c3c0..54b45593991 100644
--- a/ports/cef/interfaces/cef_response.rs
+++ b/ports/cef/interfaces/cef_response.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -122,13 +123,13 @@ pub struct _cef_response_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_response_t = _cef_response_t;
 
@@ -144,7 +145,8 @@ pub struct CefResponse {
 impl Clone for CefResponse {
   fn clone(&self) -> CefResponse{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefResponse {
@@ -157,7 +159,8 @@ impl Clone for CefResponse {
 impl Drop for CefResponse {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -172,7 +175,8 @@ impl CefResponse {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_response_t) -> CefResponse {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefResponse {
@@ -186,7 +190,8 @@ impl CefResponse {
 
   pub fn c_object_addrefed(&self) -> *mut cef_response_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -194,17 +199,18 @@ impl CefResponse {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Returns true (1) if this object is read-only.
   //
   pub fn is_read_only(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -218,7 +224,8 @@ impl CefResponse {
   // Get the response status code.
   //
   pub fn get_status(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -232,7 +239,8 @@ impl CefResponse {
   // Set the response status code.
   //
   pub fn set_status(&self, status: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -248,7 +256,8 @@ impl CefResponse {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_status_text(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -262,7 +271,8 @@ impl CefResponse {
   // Set the response status text.
   //
   pub fn set_status_text(&self, statusText: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -278,7 +288,8 @@ impl CefResponse {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_mime_type(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -292,7 +303,8 @@ impl CefResponse {
   // Set the response mime type.
   //
   pub fn set_mime_type(&self, mimeType: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -308,7 +320,8 @@ impl CefResponse {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_header(&self, name: &[u16]) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -323,7 +336,8 @@ impl CefResponse {
   // Get all response header fields.
   //
   pub fn get_header_map(&self, headerMap: HashMap<String,Vec<String>>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -338,7 +352,8 @@ impl CefResponse {
   // Set all response header fields.
   //
   pub fn set_header_map(&self, headerMap: HashMap<String,Vec<String>>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -377,7 +392,8 @@ impl CefWrap<*mut cef_response_t> for Option<CefResponse> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_response_t) -> Option<CefResponse> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefResponse::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_scheme.rs b/ports/cef/interfaces/cef_scheme.rs
index 871173b083e..2bf8a0030e3 100644
--- a/ports/cef/interfaces/cef_scheme.rs
+++ b/ports/cef/interfaces/cef_scheme.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -108,13 +109,13 @@ pub struct _cef_scheme_registrar_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_scheme_registrar_t = _cef_scheme_registrar_t;
 
@@ -129,7 +130,8 @@ pub struct CefSchemeRegistrar {
 impl Clone for CefSchemeRegistrar {
   fn clone(&self) -> CefSchemeRegistrar{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefSchemeRegistrar {
@@ -142,7 +144,8 @@ impl Clone for CefSchemeRegistrar {
 impl Drop for CefSchemeRegistrar {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -157,7 +160,8 @@ impl CefSchemeRegistrar {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_scheme_registrar_t) -> CefSchemeRegistrar {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefSchemeRegistrar {
@@ -171,7 +175,8 @@ impl CefSchemeRegistrar {
 
   pub fn c_object_addrefed(&self) -> *mut cef_scheme_registrar_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -179,10 +184,10 @@ impl CefSchemeRegistrar {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -234,7 +239,8 @@ impl CefSchemeRegistrar {
   pub fn add_custom_scheme(&self, scheme_name: &[u16], is_standard: libc::c_int,
       is_local: libc::c_int,
       is_display_isolated: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -265,7 +271,8 @@ impl CefWrap<*mut cef_scheme_registrar_t> for Option<CefSchemeRegistrar> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_scheme_registrar_t) -> Option<CefSchemeRegistrar> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefSchemeRegistrar::from_c_object_addref(c_object))
@@ -303,13 +310,13 @@ pub struct _cef_scheme_handler_factory_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_scheme_handler_factory_t = _cef_scheme_handler_factory_t;
 
@@ -326,7 +333,8 @@ pub struct CefSchemeHandlerFactory {
 impl Clone for CefSchemeHandlerFactory {
   fn clone(&self) -> CefSchemeHandlerFactory{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefSchemeHandlerFactory {
@@ -339,7 +347,8 @@ impl Clone for CefSchemeHandlerFactory {
 impl Drop for CefSchemeHandlerFactory {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -354,7 +363,8 @@ impl CefSchemeHandlerFactory {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_scheme_handler_factory_t) -> CefSchemeHandlerFactory {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefSchemeHandlerFactory {
@@ -368,7 +378,8 @@ impl CefSchemeHandlerFactory {
 
   pub fn c_object_addrefed(&self) -> *mut cef_scheme_handler_factory_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -376,10 +387,10 @@ impl CefSchemeHandlerFactory {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -393,7 +404,8 @@ impl CefSchemeHandlerFactory {
   pub fn create(&self, browser: interfaces::CefBrowser,
       frame: interfaces::CefFrame, scheme_name: &[u16],
       request: interfaces::CefRequest) -> interfaces::CefResourceHandler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -424,7 +436,8 @@ impl CefWrap<*mut cef_scheme_handler_factory_t> for Option<CefSchemeHandlerFacto
     }
   }
   unsafe fn to_rust(c_object: *mut cef_scheme_handler_factory_t) -> Option<CefSchemeHandlerFactory> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefSchemeHandlerFactory::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_ssl_info.rs b/ports/cef/interfaces/cef_ssl_info.rs
index 77b434eb5dc..d2cfcba7c59 100644
--- a/ports/cef/interfaces/cef_ssl_info.rs
+++ b/ports/cef/interfaces/cef_ssl_info.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -122,13 +123,13 @@ pub struct _cef_sslcert_principal_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_sslcert_principal_t = _cef_sslcert_principal_t;
 
@@ -143,7 +144,8 @@ pub struct CefSSLCertPrincipal {
 impl Clone for CefSSLCertPrincipal {
   fn clone(&self) -> CefSSLCertPrincipal{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefSSLCertPrincipal {
@@ -156,7 +158,8 @@ impl Clone for CefSSLCertPrincipal {
 impl Drop for CefSSLCertPrincipal {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -171,7 +174,8 @@ impl CefSSLCertPrincipal {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_sslcert_principal_t) -> CefSSLCertPrincipal {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefSSLCertPrincipal {
@@ -185,7 +189,8 @@ impl CefSSLCertPrincipal {
 
   pub fn c_object_addrefed(&self) -> *mut cef_sslcert_principal_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -193,10 +198,10 @@ impl CefSSLCertPrincipal {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -205,7 +210,8 @@ impl CefSSLCertPrincipal {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_display_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -220,7 +226,8 @@ impl CefSSLCertPrincipal {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_common_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -235,7 +242,8 @@ impl CefSSLCertPrincipal {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_locality_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -250,7 +258,8 @@ impl CefSSLCertPrincipal {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_state_or_province_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -265,7 +274,8 @@ impl CefSSLCertPrincipal {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_country_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -279,7 +289,8 @@ impl CefSSLCertPrincipal {
   // Retrieve the list of street addresses.
   //
   pub fn get_street_addresses(&self, addresses: Vec<String>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -294,7 +305,8 @@ impl CefSSLCertPrincipal {
   // Retrieve the list of organization names.
   //
   pub fn get_organization_names(&self, names: Vec<String>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -309,7 +321,8 @@ impl CefSSLCertPrincipal {
   // Retrieve the list of organization unit names.
   //
   pub fn get_organization_unit_names(&self, names: Vec<String>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -324,7 +337,8 @@ impl CefSSLCertPrincipal {
   // Retrieve the list of domain components.
   //
   pub fn get_domain_components(&self, components: Vec<String>) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -352,7 +366,8 @@ impl CefWrap<*mut cef_sslcert_principal_t> for Option<CefSSLCertPrincipal> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_sslcert_principal_t) -> Option<CefSSLCertPrincipal> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefSSLCertPrincipal::from_c_object_addref(c_object))
@@ -421,13 +436,13 @@ pub struct _cef_sslinfo_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_sslinfo_t = _cef_sslinfo_t;
 
@@ -442,7 +457,8 @@ pub struct CefSSLInfo {
 impl Clone for CefSSLInfo {
   fn clone(&self) -> CefSSLInfo{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefSSLInfo {
@@ -455,7 +471,8 @@ impl Clone for CefSSLInfo {
 impl Drop for CefSSLInfo {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -470,7 +487,8 @@ impl CefSSLInfo {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_sslinfo_t) -> CefSSLInfo {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefSSLInfo {
@@ -484,7 +502,8 @@ impl CefSSLInfo {
 
   pub fn c_object_addrefed(&self) -> *mut cef_sslinfo_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -492,10 +511,10 @@ impl CefSSLInfo {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -504,7 +523,8 @@ impl CefSSLInfo {
   // match the host name of the web server.
   //
   pub fn get_subject(&self) -> interfaces::CefSSLCertPrincipal {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -518,7 +538,8 @@ impl CefSSLInfo {
   // Returns the issuer of the X.509 certificate.
   //
   pub fn get_issuer(&self) -> interfaces::CefSSLCertPrincipal {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -533,7 +554,8 @@ impl CefSSLInfo {
   // possibly includes a leading 00 byte.
   //
   pub fn get_serial_number(&self) -> interfaces::CefBinaryValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -548,7 +570,8 @@ impl CefSSLInfo {
   // CefTime.GetTimeT() will return 0 if no date was specified.
   //
   pub fn get_valid_start(&self) -> types::cef_time_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -563,7 +586,8 @@ impl CefSSLInfo {
   // CefTime.GetTimeT() will return 0 if no date was specified.
   //
   pub fn get_valid_expiry(&self) -> types::cef_time_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -577,7 +601,8 @@ impl CefSSLInfo {
   // Returns the DER encoded data for the X.509 certificate.
   //
   pub fn get_derencoded(&self) -> interfaces::CefBinaryValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -591,7 +616,8 @@ impl CefSSLInfo {
   // Returns the PEM encoded data for the X.509 certificate.
   //
   pub fn get_pemencoded(&self) -> interfaces::CefBinaryValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -618,7 +644,8 @@ impl CefWrap<*mut cef_sslinfo_t> for Option<CefSSLInfo> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_sslinfo_t) -> Option<CefSSLInfo> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefSSLInfo::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_stream.rs b/ports/cef/interfaces/cef_stream.rs
index 598436523ca..8489931a283 100644
--- a/ports/cef/interfaces/cef_stream.rs
+++ b/ports/cef/interfaces/cef_stream.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -90,13 +91,13 @@ pub struct _cef_read_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_read_handler_t = _cef_read_handler_t;
 
@@ -112,7 +113,8 @@ pub struct CefReadHandler {
 impl Clone for CefReadHandler {
   fn clone(&self) -> CefReadHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefReadHandler {
@@ -125,7 +127,8 @@ impl Clone for CefReadHandler {
 impl Drop for CefReadHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -140,7 +143,8 @@ impl CefReadHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_read_handler_t) -> CefReadHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefReadHandler {
@@ -154,7 +158,8 @@ impl CefReadHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_read_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -162,10 +167,10 @@ impl CefReadHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -173,7 +178,8 @@ impl CefReadHandler {
   //
   pub fn read(&self, ptr: &mut (), size: libc::size_t,
       n: libc::size_t) -> libc::size_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -191,7 +197,8 @@ impl CefReadHandler {
   // SEEK_END or SEEK_SET. Return zero on success and non-zero on failure.
   //
   pub fn seek(&self, offset: i64, whence: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -207,7 +214,8 @@ impl CefReadHandler {
   // Return the current offset position.
   //
   pub fn tell(&self) -> i64 {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -221,7 +229,8 @@ impl CefReadHandler {
   // Return non-zero if at end of file.
   //
   pub fn eof(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -237,7 +246,8 @@ impl CefReadHandler {
   // the handler from.
   //
   pub fn may_block(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -264,7 +274,8 @@ impl CefWrap<*mut cef_read_handler_t> for Option<CefReadHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_read_handler_t) -> Option<CefReadHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefReadHandler::from_c_object_addref(c_object))
@@ -318,13 +329,13 @@ pub struct _cef_stream_reader_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_stream_reader_t = _cef_stream_reader_t;
 
@@ -340,7 +351,8 @@ pub struct CefStreamReader {
 impl Clone for CefStreamReader {
   fn clone(&self) -> CefStreamReader{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefStreamReader {
@@ -353,7 +365,8 @@ impl Clone for CefStreamReader {
 impl Drop for CefStreamReader {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -368,7 +381,8 @@ impl CefStreamReader {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_stream_reader_t) -> CefStreamReader {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefStreamReader {
@@ -382,7 +396,8 @@ impl CefStreamReader {
 
   pub fn c_object_addrefed(&self) -> *mut cef_stream_reader_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -390,10 +405,10 @@ impl CefStreamReader {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -401,7 +416,8 @@ impl CefStreamReader {
   //
   pub fn read(&self, ptr: &mut (), size: libc::size_t,
       n: libc::size_t) -> libc::size_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -419,7 +435,8 @@ impl CefStreamReader {
   // SEEK_END or SEEK_SET. Returns zero on success and non-zero on failure.
   //
   pub fn seek(&self, offset: i64, whence: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -435,7 +452,8 @@ impl CefStreamReader {
   // Return the current offset position.
   //
   pub fn tell(&self) -> i64 {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -449,7 +467,8 @@ impl CefStreamReader {
   // Return non-zero if at end of file.
   //
   pub fn eof(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -465,7 +484,8 @@ impl CefStreamReader {
   // the reader from.
   //
   pub fn may_block(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -528,7 +548,8 @@ impl CefWrap<*mut cef_stream_reader_t> for Option<CefStreamReader> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_stream_reader_t) -> Option<CefStreamReader> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefStreamReader::from_c_object_addref(c_object))
@@ -583,13 +604,13 @@ pub struct _cef_write_handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_write_handler_t = _cef_write_handler_t;
 
@@ -605,7 +626,8 @@ pub struct CefWriteHandler {
 impl Clone for CefWriteHandler {
   fn clone(&self) -> CefWriteHandler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefWriteHandler {
@@ -618,7 +640,8 @@ impl Clone for CefWriteHandler {
 impl Drop for CefWriteHandler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -633,7 +656,8 @@ impl CefWriteHandler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_write_handler_t) -> CefWriteHandler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefWriteHandler {
@@ -647,7 +671,8 @@ impl CefWriteHandler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_write_handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -655,10 +680,10 @@ impl CefWriteHandler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -666,7 +691,8 @@ impl CefWriteHandler {
   //
   pub fn write(&self, ptr: &(), size: libc::size_t,
       n: libc::size_t) -> libc::size_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -684,7 +710,8 @@ impl CefWriteHandler {
   // SEEK_END or SEEK_SET. Return zero on success and non-zero on failure.
   //
   pub fn seek(&self, offset: i64, whence: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -700,7 +727,8 @@ impl CefWriteHandler {
   // Return the current offset position.
   //
   pub fn tell(&self) -> i64 {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -714,7 +742,8 @@ impl CefWriteHandler {
   // Flush the stream.
   //
   pub fn flush(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -730,7 +759,8 @@ impl CefWriteHandler {
   // the handler from.
   //
   pub fn may_block(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -757,7 +787,8 @@ impl CefWrap<*mut cef_write_handler_t> for Option<CefWriteHandler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_write_handler_t) -> Option<CefWriteHandler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefWriteHandler::from_c_object_addref(c_object))
@@ -812,13 +843,13 @@ pub struct _cef_stream_writer_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_stream_writer_t = _cef_stream_writer_t;
 
@@ -834,7 +865,8 @@ pub struct CefStreamWriter {
 impl Clone for CefStreamWriter {
   fn clone(&self) -> CefStreamWriter{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefStreamWriter {
@@ -847,7 +879,8 @@ impl Clone for CefStreamWriter {
 impl Drop for CefStreamWriter {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -862,7 +895,8 @@ impl CefStreamWriter {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_stream_writer_t) -> CefStreamWriter {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefStreamWriter {
@@ -876,7 +910,8 @@ impl CefStreamWriter {
 
   pub fn c_object_addrefed(&self) -> *mut cef_stream_writer_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -884,10 +919,10 @@ impl CefStreamWriter {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -895,7 +930,8 @@ impl CefStreamWriter {
   //
   pub fn write(&self, ptr: &(), size: libc::size_t,
       n: libc::size_t) -> libc::size_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -913,7 +949,8 @@ impl CefStreamWriter {
   // SEEK_END or SEEK_SET. Returns zero on success and non-zero on failure.
   //
   pub fn seek(&self, offset: i64, whence: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -929,7 +966,8 @@ impl CefStreamWriter {
   // Return the current offset position.
   //
   pub fn tell(&self) -> i64 {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -943,7 +981,8 @@ impl CefStreamWriter {
   // Flush the stream.
   //
   pub fn flush(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -959,7 +998,8 @@ impl CefStreamWriter {
   // the writer from.
   //
   pub fn may_block(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1009,7 +1049,8 @@ impl CefWrap<*mut cef_stream_writer_t> for Option<CefStreamWriter> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_stream_writer_t) -> Option<CefStreamWriter> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefStreamWriter::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_string_visitor.rs b/ports/cef/interfaces/cef_string_visitor.rs
index e28c3f016d6..f895aa70643 100644
--- a/ports/cef/interfaces/cef_string_visitor.rs
+++ b/ports/cef/interfaces/cef_string_visitor.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -64,13 +65,13 @@ pub struct _cef_string_visitor_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_string_visitor_t = _cef_string_visitor_t;
 
@@ -85,7 +86,8 @@ pub struct CefStringVisitor {
 impl Clone for CefStringVisitor {
   fn clone(&self) -> CefStringVisitor{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefStringVisitor {
@@ -98,7 +100,8 @@ impl Clone for CefStringVisitor {
 impl Drop for CefStringVisitor {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -113,7 +116,8 @@ impl CefStringVisitor {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_string_visitor_t) -> CefStringVisitor {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefStringVisitor {
@@ -127,7 +131,8 @@ impl CefStringVisitor {
 
   pub fn c_object_addrefed(&self) -> *mut cef_string_visitor_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -135,17 +140,18 @@ impl CefStringVisitor {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Method that will be executed.
   //
   pub fn visit(&self, string: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -173,7 +179,8 @@ impl CefWrap<*mut cef_string_visitor_t> for Option<CefStringVisitor> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_string_visitor_t) -> Option<CefStringVisitor> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefStringVisitor::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_task.rs b/ports/cef/interfaces/cef_task.rs
index aa94aebd23f..762bcf65362 100644
--- a/ports/cef/interfaces/cef_task.rs
+++ b/ports/cef/interfaces/cef_task.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -68,13 +69,13 @@ pub struct _cef_task_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_task_t = _cef_task_t;
 
@@ -94,7 +95,8 @@ pub struct CefTask {
 impl Clone for CefTask {
   fn clone(&self) -> CefTask{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefTask {
@@ -107,7 +109,8 @@ impl Clone for CefTask {
 impl Drop for CefTask {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -122,7 +125,8 @@ impl CefTask {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_task_t) -> CefTask {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefTask {
@@ -136,7 +140,8 @@ impl CefTask {
 
   pub fn c_object_addrefed(&self) -> *mut cef_task_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -144,17 +149,18 @@ impl CefTask {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
   // Method that will be executed on the target thread.
   //
   pub fn execute(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -181,7 +187,8 @@ impl CefWrap<*mut cef_task_t> for Option<CefTask> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_task_t) -> Option<CefTask> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefTask::from_c_object_addref(c_object))
@@ -244,13 +251,13 @@ pub struct _cef_task_runner_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_task_runner_t = _cef_task_runner_t;
 
@@ -271,7 +278,8 @@ pub struct CefTaskRunner {
 impl Clone for CefTaskRunner {
   fn clone(&self) -> CefTaskRunner{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefTaskRunner {
@@ -284,7 +292,8 @@ impl Clone for CefTaskRunner {
 impl Drop for CefTaskRunner {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -299,7 +308,8 @@ impl CefTaskRunner {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_task_runner_t) -> CefTaskRunner {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefTaskRunner {
@@ -313,7 +323,8 @@ impl CefTaskRunner {
 
   pub fn c_object_addrefed(&self) -> *mut cef_task_runner_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -321,10 +332,10 @@ impl CefTaskRunner {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -332,7 +343,8 @@ impl CefTaskRunner {
   // |that| object.
   //
   pub fn is_same(&self, that: interfaces::CefTaskRunner) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -347,7 +359,8 @@ impl CefTaskRunner {
   // Returns true (1) if this task runner belongs to the current thread.
   //
   pub fn belongs_to_current_thread(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -362,7 +375,8 @@ impl CefTaskRunner {
   //
   pub fn belongs_to_thread(&self,
       threadId: types::cef_thread_id_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -378,7 +392,8 @@ impl CefTaskRunner {
   // Execution will occur asynchronously.
   //
   pub fn post_task(&self, task: interfaces::CefTask) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -397,7 +412,8 @@ impl CefTaskRunner {
   //
   pub fn post_delayed_task(&self, task: interfaces::CefTask,
       delay_ms: i64) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -451,7 +467,8 @@ impl CefWrap<*mut cef_task_runner_t> for Option<CefTaskRunner> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_task_runner_t) -> Option<CefTaskRunner> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefTaskRunner::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_trace.rs b/ports/cef/interfaces/cef_trace.rs
index b954cef0e50..2a1793864bb 100644
--- a/ports/cef/interfaces/cef_trace.rs
+++ b/ports/cef/interfaces/cef_trace.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -69,13 +70,13 @@ pub struct _cef_end_tracing_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_end_tracing_callback_t = _cef_end_tracing_callback_t;
 
@@ -92,7 +93,8 @@ pub struct CefEndTracingCallback {
 impl Clone for CefEndTracingCallback {
   fn clone(&self) -> CefEndTracingCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefEndTracingCallback {
@@ -105,7 +107,8 @@ impl Clone for CefEndTracingCallback {
 impl Drop for CefEndTracingCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -120,7 +123,8 @@ impl CefEndTracingCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_end_tracing_callback_t) -> CefEndTracingCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefEndTracingCallback {
@@ -134,7 +138,8 @@ impl CefEndTracingCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_end_tracing_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -142,10 +147,10 @@ impl CefEndTracingCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -154,7 +159,8 @@ impl CefEndTracingCallback {
   // deleting |tracing_file|.
   //
   pub fn on_end_tracing_complete(&self, tracing_file: &[u16]) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -182,7 +188,8 @@ impl CefWrap<*mut cef_end_tracing_callback_t> for Option<CefEndTracingCallback>
     }
   }
   unsafe fn to_rust(c_object: *mut cef_end_tracing_callback_t) -> Option<CefEndTracingCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefEndTracingCallback::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_urlrequest.rs b/ports/cef/interfaces/cef_urlrequest.rs
index 7bbd7f84e2f..deec0bcdd6b 100644
--- a/ports/cef/interfaces/cef_urlrequest.rs
+++ b/ports/cef/interfaces/cef_urlrequest.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -101,13 +102,13 @@ pub struct _cef_urlrequest_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_urlrequest_t = _cef_urlrequest_t;
 
@@ -126,7 +127,8 @@ pub struct CefURLRequest {
 impl Clone for CefURLRequest {
   fn clone(&self) -> CefURLRequest{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefURLRequest {
@@ -139,7 +141,8 @@ impl Clone for CefURLRequest {
 impl Drop for CefURLRequest {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -154,7 +157,8 @@ impl CefURLRequest {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_urlrequest_t) -> CefURLRequest {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefURLRequest {
@@ -168,7 +172,8 @@ impl CefURLRequest {
 
   pub fn c_object_addrefed(&self) -> *mut cef_urlrequest_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -176,10 +181,10 @@ impl CefURLRequest {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -187,7 +192,8 @@ impl CefURLRequest {
   // object is read-only and should not be modified.
   //
   pub fn get_request(&self) -> interfaces::CefRequest {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -201,7 +207,8 @@ impl CefURLRequest {
   // Returns the client.
   //
   pub fn get_client(&self) -> interfaces::CefURLRequestClient {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -215,7 +222,8 @@ impl CefURLRequest {
   // Returns the request status.
   //
   pub fn get_request_status(&self) -> types::cef_urlrequest_status_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -230,7 +238,8 @@ impl CefURLRequest {
   // otherwise.
   //
   pub fn get_request_error(&self) -> types::cef_errorcode_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -246,7 +255,8 @@ impl CefURLRequest {
   // The returned object is read-only and should not be modified.
   //
   pub fn get_response(&self) -> interfaces::CefResponse {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -260,7 +270,8 @@ impl CefURLRequest {
   // Cancel the request.
   //
   pub fn cancel(&self) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -314,7 +325,8 @@ impl CefWrap<*mut cef_urlrequest_t> for Option<CefURLRequest> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_urlrequest_t) -> Option<CefURLRequest> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefURLRequest::from_c_object_addref(c_object))
@@ -392,13 +404,13 @@ pub struct _cef_urlrequest_client_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_urlrequest_client_t = _cef_urlrequest_client_t;
 
@@ -415,7 +427,8 @@ pub struct CefURLRequestClient {
 impl Clone for CefURLRequestClient {
   fn clone(&self) -> CefURLRequestClient{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefURLRequestClient {
@@ -428,7 +441,8 @@ impl Clone for CefURLRequestClient {
 impl Drop for CefURLRequestClient {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -443,7 +457,8 @@ impl CefURLRequestClient {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_urlrequest_client_t) -> CefURLRequestClient {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefURLRequestClient {
@@ -457,7 +472,8 @@ impl CefURLRequestClient {
 
   pub fn c_object_addrefed(&self) -> *mut cef_urlrequest_client_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -465,10 +481,10 @@ impl CefURLRequestClient {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -477,7 +493,8 @@ impl CefURLRequestClient {
   // successful or not.
   //
   pub fn on_request_complete(&self, request: interfaces::CefURLRequest) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -496,7 +513,8 @@ impl CefURLRequestClient {
   //
   pub fn on_upload_progress(&self, request: interfaces::CefURLRequest,
       current: i64, total: i64) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -516,7 +534,8 @@ impl CefURLRequestClient {
   //
   pub fn on_download_progress(&self, request: interfaces::CefURLRequest,
       current: i64, total: i64) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -536,7 +555,8 @@ impl CefURLRequestClient {
   //
   pub fn on_download_data(&self, request: interfaces::CefURLRequest, data: &(),
       data_length: libc::size_t) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -561,7 +581,8 @@ impl CefURLRequestClient {
   pub fn get_auth_credentials(&self, isProxy: libc::c_int, host: &[u16],
       port: libc::c_int, realm: &[u16], scheme: &[u16],
       callback: interfaces::CefAuthCallback) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -594,7 +615,8 @@ impl CefWrap<*mut cef_urlrequest_client_t> for Option<CefURLRequestClient> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_urlrequest_client_t) -> Option<CefURLRequestClient> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefURLRequestClient::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_v8.rs b/ports/cef/interfaces/cef_v8.rs
index 8f8db1ae171..efe234b92a3 100644
--- a/ports/cef/interfaces/cef_v8.rs
+++ b/ports/cef/interfaces/cef_v8.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -131,13 +132,13 @@ pub struct _cef_v8context_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_v8context_t = _cef_v8context_t;
 
@@ -156,7 +157,8 @@ pub struct CefV8Context {
 impl Clone for CefV8Context {
   fn clone(&self) -> CefV8Context{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefV8Context {
@@ -169,7 +171,8 @@ impl Clone for CefV8Context {
 impl Drop for CefV8Context {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -184,7 +187,8 @@ impl CefV8Context {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_v8context_t) -> CefV8Context {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefV8Context {
@@ -198,7 +202,8 @@ impl CefV8Context {
 
   pub fn c_object_addrefed(&self) -> *mut cef_v8context_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -206,10 +211,10 @@ impl CefV8Context {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -218,7 +223,8 @@ impl CefV8Context {
   // called on any render process thread.
   //
   pub fn get_task_runner(&self) -> interfaces::CefTaskRunner {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -234,7 +240,8 @@ impl CefV8Context {
   // returns false (0).
   //
   pub fn is_valid(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -249,7 +256,8 @@ impl CefV8Context {
   // reference for WebWorker contexts.
   //
   pub fn get_browser(&self) -> interfaces::CefBrowser {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -264,7 +272,8 @@ impl CefV8Context {
   // reference for WebWorker contexts.
   //
   pub fn get_frame(&self) -> interfaces::CefFrame {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -279,7 +288,8 @@ impl CefV8Context {
   // before calling this function.
   //
   pub fn get_global(&self) -> interfaces::CefV8Value {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -297,7 +307,8 @@ impl CefV8Context {
   // if the scope was entered successfully.
   //
   pub fn enter(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -312,7 +323,8 @@ impl CefV8Context {
   // true (1) if the scope was exited successfully.
   //
   pub fn exit(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -327,7 +339,8 @@ impl CefV8Context {
   // object.
   //
   pub fn is_same(&self, that: interfaces::CefV8Context) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -346,7 +359,8 @@ impl CefV8Context {
   //
   pub fn eval(&self, code: &[u16], retval: interfaces::CefV8Value,
       exception: interfaces::CefV8Exception) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -409,7 +423,8 @@ impl CefWrap<*mut cef_v8context_t> for Option<CefV8Context> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_v8context_t) -> Option<CefV8Context> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefV8Context::from_c_object_addref(c_object))
@@ -447,13 +462,13 @@ pub struct _cef_v8handler_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_v8handler_t = _cef_v8handler_t;
 
@@ -470,7 +485,8 @@ pub struct CefV8Handler {
 impl Clone for CefV8Handler {
   fn clone(&self) -> CefV8Handler{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefV8Handler {
@@ -483,7 +499,8 @@ impl Clone for CefV8Handler {
 impl Drop for CefV8Handler {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -498,7 +515,8 @@ impl CefV8Handler {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_v8handler_t) -> CefV8Handler {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefV8Handler {
@@ -512,7 +530,8 @@ impl CefV8Handler {
 
   pub fn c_object_addrefed(&self) -> *mut cef_v8handler_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -520,10 +539,10 @@ impl CefV8Handler {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -537,7 +556,8 @@ impl CefV8Handler {
       arguments_count: libc::size_t, arguments: *const interfaces::CefV8Value,
       retval: interfaces::CefV8Value,
       exception: *mut types::cef_string_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -570,7 +590,8 @@ impl CefWrap<*mut cef_v8handler_t> for Option<CefV8Handler> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_v8handler_t) -> Option<CefV8Handler> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefV8Handler::from_c_object_addref(c_object))
@@ -619,13 +640,13 @@ pub struct _cef_v8accessor_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_v8accessor_t = _cef_v8accessor_t;
 
@@ -643,7 +664,8 @@ pub struct CefV8Accessor {
 impl Clone for CefV8Accessor {
   fn clone(&self) -> CefV8Accessor{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefV8Accessor {
@@ -656,7 +678,8 @@ impl Clone for CefV8Accessor {
 impl Drop for CefV8Accessor {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -671,7 +694,8 @@ impl CefV8Accessor {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_v8accessor_t) -> CefV8Accessor {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefV8Accessor {
@@ -685,7 +709,8 @@ impl CefV8Accessor {
 
   pub fn c_object_addrefed(&self) -> *mut cef_v8accessor_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -693,10 +718,10 @@ impl CefV8Accessor {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -709,7 +734,8 @@ impl CefV8Accessor {
   pub fn get(&self, name: &[u16], object: interfaces::CefV8Value,
       retval: interfaces::CefV8Value,
       exception: *mut types::cef_string_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -733,7 +759,8 @@ impl CefV8Accessor {
   pub fn set(&self, name: &[u16], object: interfaces::CefV8Value,
       value: interfaces::CefV8Value,
       exception: *mut types::cef_string_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -764,7 +791,8 @@ impl CefWrap<*mut cef_v8accessor_t> for Option<CefV8Accessor> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_v8accessor_t) -> Option<CefV8Accessor> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefV8Accessor::from_c_object_addref(c_object))
@@ -844,13 +872,13 @@ pub struct _cef_v8exception_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_v8exception_t = _cef_v8exception_t;
 
@@ -866,7 +894,8 @@ pub struct CefV8Exception {
 impl Clone for CefV8Exception {
   fn clone(&self) -> CefV8Exception{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefV8Exception {
@@ -879,7 +908,8 @@ impl Clone for CefV8Exception {
 impl Drop for CefV8Exception {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -894,7 +924,8 @@ impl CefV8Exception {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_v8exception_t) -> CefV8Exception {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefV8Exception {
@@ -908,7 +939,8 @@ impl CefV8Exception {
 
   pub fn c_object_addrefed(&self) -> *mut cef_v8exception_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -916,10 +948,10 @@ impl CefV8Exception {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -927,7 +959,8 @@ impl CefV8Exception {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_message(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -942,7 +975,8 @@ impl CefV8Exception {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_source_line(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -958,7 +992,8 @@ impl CefV8Exception {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_script_resource_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -973,7 +1008,8 @@ impl CefV8Exception {
   // line number is unknown.
   //
   pub fn get_line_number(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -988,7 +1024,8 @@ impl CefV8Exception {
   // occurred.
   //
   pub fn get_start_position(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1003,7 +1040,8 @@ impl CefV8Exception {
   // occurred.
   //
   pub fn get_end_position(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1018,7 +1056,8 @@ impl CefV8Exception {
   // occurred.
   //
   pub fn get_start_column(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1033,7 +1072,8 @@ impl CefV8Exception {
   // occurred.
   //
   pub fn get_end_column(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1060,7 +1100,8 @@ impl CefWrap<*mut cef_v8exception_t> for Option<CefV8Exception> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_v8exception_t) -> Option<CefV8Exception> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefV8Exception::from_c_object_addref(c_object))
@@ -1416,13 +1457,13 @@ pub struct _cef_v8value_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_v8value_t = _cef_v8value_t;
 
@@ -1441,7 +1482,8 @@ pub struct CefV8Value {
 impl Clone for CefV8Value {
   fn clone(&self) -> CefV8Value{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefV8Value {
@@ -1454,7 +1496,8 @@ impl Clone for CefV8Value {
 impl Drop for CefV8Value {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -1469,7 +1512,8 @@ impl CefV8Value {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_v8value_t) -> CefV8Value {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefV8Value {
@@ -1483,7 +1527,8 @@ impl CefV8Value {
 
   pub fn c_object_addrefed(&self) -> *mut cef_v8value_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -1491,10 +1536,10 @@ impl CefV8Value {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -1503,7 +1548,8 @@ impl CefV8Value {
   // returns false (0).
   //
   pub fn is_valid(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1517,7 +1563,8 @@ impl CefV8Value {
   // True if the value type is undefined.
   //
   pub fn is_undefined(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1531,7 +1578,8 @@ impl CefV8Value {
   // True if the value type is null.
   //
   pub fn is_null(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1545,7 +1593,8 @@ impl CefV8Value {
   // True if the value type is bool.
   //
   pub fn is_bool(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1559,7 +1608,8 @@ impl CefV8Value {
   // True if the value type is int.
   //
   pub fn is_int(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1573,7 +1623,8 @@ impl CefV8Value {
   // True if the value type is unsigned int.
   //
   pub fn is_uint(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1587,7 +1638,8 @@ impl CefV8Value {
   // True if the value type is double.
   //
   pub fn is_double(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1601,7 +1653,8 @@ impl CefV8Value {
   // True if the value type is Date.
   //
   pub fn is_date(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1615,7 +1668,8 @@ impl CefV8Value {
   // True if the value type is string.
   //
   pub fn is_string(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1629,7 +1683,8 @@ impl CefV8Value {
   // True if the value type is object.
   //
   pub fn is_object(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1643,7 +1698,8 @@ impl CefV8Value {
   // True if the value type is array.
   //
   pub fn is_array(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1657,7 +1713,8 @@ impl CefV8Value {
   // True if the value type is function.
   //
   pub fn is_function(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1672,7 +1729,8 @@ impl CefV8Value {
   // object.
   //
   pub fn is_same(&self, that: interfaces::CefV8Value) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1688,7 +1746,8 @@ impl CefV8Value {
   // necessary.
   //
   pub fn get_bool_value(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1703,7 +1762,8 @@ impl CefV8Value {
   // necessary.
   //
   pub fn get_int_value(&self) -> i32 {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1718,7 +1778,8 @@ impl CefV8Value {
   // necessary.
   //
   pub fn get_uint_value(&self) -> u32 {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1733,7 +1794,8 @@ impl CefV8Value {
   // necessary.
   //
   pub fn get_double_value(&self) -> libc::c_double {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1748,7 +1810,8 @@ impl CefV8Value {
   // necessary.
   //
   pub fn get_date_value(&self) -> types::cef_time_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1764,7 +1827,8 @@ impl CefV8Value {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_string_value(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1783,7 +1847,8 @@ impl CefV8Value {
   // Returns true (1) if this is a user created object.
   //
   pub fn is_user_created(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1798,7 +1863,8 @@ impl CefV8Value {
   // attribute exists only in the scope of the current CEF value object.
   //
   pub fn has_exception(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1813,7 +1879,8 @@ impl CefV8Value {
   // exists only in the scope of the current CEF value object.
   //
   pub fn get_exception(&self) -> interfaces::CefV8Exception {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1827,7 +1894,8 @@ impl CefV8Value {
   // Clears the last exception and returns true (1) on success.
   //
   pub fn clear_exception(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1842,7 +1910,8 @@ impl CefV8Value {
   // attribute exists only in the scope of the current CEF value object.
   //
   pub fn will_rethrow_exceptions(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1860,7 +1929,8 @@ impl CefV8Value {
   // exists only in the scope of the current CEF value object.
   //
   pub fn set_rethrow_exceptions(&self, rethrow: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1875,7 +1945,8 @@ impl CefV8Value {
   // Returns true (1) if the object has a value with the specified identifier.
   //
   pub fn has_value_bykey(&self, key: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1890,7 +1961,8 @@ impl CefV8Value {
   // Returns true (1) if the object has a value with the specified identifier.
   //
   pub fn has_value_byindex(&self, index: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1908,7 +1980,8 @@ impl CefV8Value {
   // will return true (1) even though deletion failed.
   //
   pub fn delete_value_bykey(&self, key: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1926,7 +1999,8 @@ impl CefV8Value {
   // function will return true (1) even though deletion failed.
   //
   pub fn delete_value_byindex(&self, index: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1942,7 +2016,8 @@ impl CefV8Value {
   // this function is called incorrectly or an exception is thrown.
   //
   pub fn get_value_bykey(&self, key: &[u16]) -> interfaces::CefV8Value {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1959,7 +2034,8 @@ impl CefV8Value {
   //
   pub fn get_value_byindex(&self,
       index: libc::c_int) -> interfaces::CefV8Value {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1978,7 +2054,8 @@ impl CefV8Value {
   //
   pub fn set_value_bykey(&self, key: &[u16], value: interfaces::CefV8Value,
       attribute: types::cef_v8_propertyattribute_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1999,7 +2076,8 @@ impl CefV8Value {
   //
   pub fn set_value_byindex(&self, index: libc::c_int,
       value: interfaces::CefV8Value) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2021,7 +2099,8 @@ impl CefV8Value {
   pub fn set_value_byaccessor(&self, key: &[u16],
       settings: types::cef_v8_accesscontrol_t,
       attribute: types::cef_v8_propertyattribute_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2039,7 +2118,8 @@ impl CefV8Value {
   // based keys will also be returned as strings.
   //
   pub fn get_keys(&self, keys: Vec<String>) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2056,7 +2136,8 @@ impl CefV8Value {
   // called on user created objects.
   //
   pub fn set_user_data(&self, user_data: interfaces::CefBase) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2071,7 +2152,8 @@ impl CefV8Value {
   // Returns the user data, if any, assigned to this object.
   //
   pub fn get_user_data(&self) -> interfaces::CefBase {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2086,7 +2168,8 @@ impl CefV8Value {
   // object.
   //
   pub fn get_externally_allocated_memory(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2109,7 +2192,8 @@ impl CefV8Value {
   //
   pub fn adjust_externally_allocated_memory(&self,
       change_in_bytes: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2127,7 +2211,8 @@ impl CefV8Value {
   // Returns the number of elements in the array.
   //
   pub fn get_array_length(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2145,7 +2230,8 @@ impl CefV8Value {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_function_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2159,7 +2245,8 @@ impl CefV8Value {
   // Returns the function handler or NULL if not a CEF-created function.
   //
   pub fn get_function_handler(&self) -> interfaces::CefV8Handler {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2183,7 +2270,8 @@ impl CefV8Value {
   pub fn execute_function(&self, object: interfaces::CefV8Value,
       arguments_count: libc::size_t,
       arguments: *const interfaces::CefV8Value) -> interfaces::CefV8Value {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2207,7 +2295,8 @@ impl CefV8Value {
   pub fn execute_function_with_context(&self, context: interfaces::CefV8Context,
       object: interfaces::CefV8Value, arguments_count: libc::size_t,
       arguments: *const interfaces::CefV8Value) -> interfaces::CefV8Value {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2377,7 +2466,8 @@ impl CefWrap<*mut cef_v8value_t> for Option<CefV8Value> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_v8value_t) -> Option<CefV8Value> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefV8Value::from_c_object_addref(c_object))
@@ -2423,13 +2513,13 @@ pub struct _cef_v8stack_trace_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_v8stack_trace_t = _cef_v8stack_trace_t;
 
@@ -2448,7 +2538,8 @@ pub struct CefV8StackTrace {
 impl Clone for CefV8StackTrace {
   fn clone(&self) -> CefV8StackTrace{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefV8StackTrace {
@@ -2461,7 +2552,8 @@ impl Clone for CefV8StackTrace {
 impl Drop for CefV8StackTrace {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -2476,7 +2568,8 @@ impl CefV8StackTrace {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_v8stack_trace_t) -> CefV8StackTrace {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefV8StackTrace {
@@ -2490,7 +2583,8 @@ impl CefV8StackTrace {
 
   pub fn c_object_addrefed(&self) -> *mut cef_v8stack_trace_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -2498,10 +2592,10 @@ impl CefV8StackTrace {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -2510,7 +2604,8 @@ impl CefV8StackTrace {
   // returns false (0).
   //
   pub fn is_valid(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2524,7 +2619,8 @@ impl CefV8StackTrace {
   // Returns the number of stack frames.
   //
   pub fn get_frame_count(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2538,7 +2634,8 @@ impl CefV8StackTrace {
   // Returns the stack frame at the specified 0-based index.
   //
   pub fn get_frame(&self, index: libc::c_int) -> interfaces::CefV8StackFrame {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2578,7 +2675,8 @@ impl CefWrap<*mut cef_v8stack_trace_t> for Option<CefV8StackTrace> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_v8stack_trace_t) -> Option<CefV8StackTrace> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefV8StackTrace::from_c_object_addref(c_object))
@@ -2660,13 +2758,13 @@ pub struct _cef_v8stack_frame_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_v8stack_frame_t = _cef_v8stack_frame_t;
 
@@ -2685,7 +2783,8 @@ pub struct CefV8StackFrame {
 impl Clone for CefV8StackFrame {
   fn clone(&self) -> CefV8StackFrame{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefV8StackFrame {
@@ -2698,7 +2797,8 @@ impl Clone for CefV8StackFrame {
 impl Drop for CefV8StackFrame {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -2713,7 +2813,8 @@ impl CefV8StackFrame {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_v8stack_frame_t) -> CefV8StackFrame {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefV8StackFrame {
@@ -2727,7 +2828,8 @@ impl CefV8StackFrame {
 
   pub fn c_object_addrefed(&self) -> *mut cef_v8stack_frame_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -2735,10 +2837,10 @@ impl CefV8StackFrame {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -2747,7 +2849,8 @@ impl CefV8StackFrame {
   // returns false (0).
   //
   pub fn is_valid(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2762,7 +2865,8 @@ impl CefV8StackFrame {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_script_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2779,7 +2883,8 @@ impl CefV8StackFrame {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_script_name_or_source_url(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2794,7 +2899,8 @@ impl CefV8StackFrame {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_function_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2808,7 +2914,8 @@ impl CefV8StackFrame {
   // Returns the 1-based line number for the function call or 0 if unknown.
   //
   pub fn get_line_number(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2823,7 +2930,8 @@ impl CefV8StackFrame {
   // unknown.
   //
   pub fn get_column(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2837,7 +2945,8 @@ impl CefV8StackFrame {
   // Returns true (1) if the function was compiled using eval().
   //
   pub fn is_eval(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2851,7 +2960,8 @@ impl CefV8StackFrame {
   // Returns true (1) if the function was called as a constructor via "new".
   //
   pub fn is_constructor(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2878,7 +2988,8 @@ impl CefWrap<*mut cef_v8stack_frame_t> for Option<CefV8StackFrame> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_v8stack_frame_t) -> Option<CefV8StackFrame> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefV8StackFrame::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_values.rs b/ports/cef/interfaces/cef_values.rs
index 84e38403b5f..398ae37b782 100644
--- a/ports/cef/interfaces/cef_values.rs
+++ b/ports/cef/interfaces/cef_values.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -223,13 +224,13 @@ pub struct _cef_value_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_value_t = _cef_value_t;
 
@@ -246,7 +247,8 @@ pub struct CefValue {
 impl Clone for CefValue {
   fn clone(&self) -> CefValue{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefValue {
@@ -259,7 +261,8 @@ impl Clone for CefValue {
 impl Drop for CefValue {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -274,7 +277,8 @@ impl CefValue {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_value_t) -> CefValue {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefValue {
@@ -288,7 +292,8 @@ impl CefValue {
 
   pub fn c_object_addrefed(&self) -> *mut cef_value_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -296,10 +301,10 @@ impl CefValue {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -311,7 +316,8 @@ impl CefValue {
   // invalid.
   //
   pub fn is_valid(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -325,7 +331,8 @@ impl CefValue {
   // Returns true (1) if the underlying data is owned by another object.
   //
   pub fn is_owned(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -340,7 +347,8 @@ impl CefValue {
   // read-only objects.
   //
   pub fn is_read_only(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -356,7 +364,8 @@ impl CefValue {
   // object and vice-versa.
   //
   pub fn is_same(&self, that: interfaces::CefValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -372,7 +381,8 @@ impl CefValue {
   // underlying value but are not necessarily the same object.
   //
   pub fn is_equal(&self, that: interfaces::CefValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -387,7 +397,8 @@ impl CefValue {
   // Returns a copy of this object. The underlying data will also be copied.
   //
   pub fn copy(&self) -> interfaces::CefValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -401,7 +412,8 @@ impl CefValue {
   // Returns the underlying value type.
   //
   pub fn get_type(&self) -> interfaces::CefValueType {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -415,7 +427,8 @@ impl CefValue {
   // Returns the underlying value as type bool.
   //
   pub fn get_bool(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -429,7 +442,8 @@ impl CefValue {
   // Returns the underlying value as type int.
   //
   pub fn get_int(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -443,7 +457,8 @@ impl CefValue {
   // Returns the underlying value as type double.
   //
   pub fn get_double(&self) -> libc::c_double {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -458,7 +473,8 @@ impl CefValue {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_string(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -477,7 +493,8 @@ impl CefValue {
   // set_binary().
   //
   pub fn get_binary(&self) -> interfaces::CefBinaryValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -496,7 +513,8 @@ impl CefValue {
   // set_dictionary().
   //
   pub fn get_dictionary(&self) -> interfaces::CefDictionaryValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -515,7 +533,8 @@ impl CefValue {
   // set_list().
   //
   pub fn get_list(&self) -> interfaces::CefListValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -530,7 +549,8 @@ impl CefValue {
   // set successfully.
   //
   pub fn set_null(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -545,7 +565,8 @@ impl CefValue {
   // set successfully.
   //
   pub fn set_bool(&self, value: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -561,7 +582,8 @@ impl CefValue {
   // set successfully.
   //
   pub fn set_int(&self, value: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -577,7 +599,8 @@ impl CefValue {
   // set successfully.
   //
   pub fn set_double(&self, value: libc::c_double) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -593,7 +616,8 @@ impl CefValue {
   // set successfully.
   //
   pub fn set_string(&self, value: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -610,7 +634,8 @@ impl CefValue {
   // the underlying data remains unchanged.
   //
   pub fn set_binary(&self, value: interfaces::CefBinaryValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -628,7 +653,8 @@ impl CefValue {
   //
   pub fn set_dictionary(&self,
       value: interfaces::CefDictionaryValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -645,7 +671,8 @@ impl CefValue {
   // the underlying data remains unchanged.
   //
   pub fn set_list(&self, value: interfaces::CefListValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -684,7 +711,8 @@ impl CefWrap<*mut cef_value_t> for Option<CefValue> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_value_t) -> Option<CefValue> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefValue::from_c_object_addref(c_object))
@@ -755,13 +783,13 @@ pub struct _cef_binary_value_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_binary_value_t = _cef_binary_value_t;
 
@@ -776,7 +804,8 @@ pub struct CefBinaryValue {
 impl Clone for CefBinaryValue {
   fn clone(&self) -> CefBinaryValue{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefBinaryValue {
@@ -789,7 +818,8 @@ impl Clone for CefBinaryValue {
 impl Drop for CefBinaryValue {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -804,7 +834,8 @@ impl CefBinaryValue {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_binary_value_t) -> CefBinaryValue {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefBinaryValue {
@@ -818,7 +849,8 @@ impl CefBinaryValue {
 
   pub fn c_object_addrefed(&self) -> *mut cef_binary_value_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -826,10 +858,10 @@ impl CefBinaryValue {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -839,7 +871,8 @@ impl CefBinaryValue {
   // functions if this function returns false (0).
   //
   pub fn is_valid(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -853,7 +886,8 @@ impl CefBinaryValue {
   // Returns true (1) if this object is currently owned by another object.
   //
   pub fn is_owned(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -868,7 +902,8 @@ impl CefBinaryValue {
   // data.
   //
   pub fn is_same(&self, that: interfaces::CefBinaryValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -884,7 +919,8 @@ impl CefBinaryValue {
   // underlying value but are not necessarily the same object.
   //
   pub fn is_equal(&self, that: interfaces::CefBinaryValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -899,7 +935,8 @@ impl CefBinaryValue {
   // Returns a copy of this object. The data in this object will also be copied.
   //
   pub fn copy(&self) -> interfaces::CefBinaryValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -913,7 +950,8 @@ impl CefBinaryValue {
   // Returns the data size.
   //
   pub fn get_size(&self) -> libc::size_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -929,7 +967,8 @@ impl CefBinaryValue {
   //
   pub fn get_data(&self, buffer: &mut (), buffer_size: libc::size_t,
       data_offset: libc::size_t) -> libc::size_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -973,7 +1012,8 @@ impl CefWrap<*mut cef_binary_value_t> for Option<CefBinaryValue> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_binary_value_t) -> Option<CefBinaryValue> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefBinaryValue::from_c_object_addref(c_object))
@@ -1216,13 +1256,13 @@ pub struct _cef_dictionary_value_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_dictionary_value_t = _cef_dictionary_value_t;
 
@@ -1238,7 +1278,8 @@ pub struct CefDictionaryValue {
 impl Clone for CefDictionaryValue {
   fn clone(&self) -> CefDictionaryValue{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefDictionaryValue {
@@ -1251,7 +1292,8 @@ impl Clone for CefDictionaryValue {
 impl Drop for CefDictionaryValue {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -1266,7 +1308,8 @@ impl CefDictionaryValue {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_dictionary_value_t) -> CefDictionaryValue {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefDictionaryValue {
@@ -1280,7 +1323,8 @@ impl CefDictionaryValue {
 
   pub fn c_object_addrefed(&self) -> *mut cef_dictionary_value_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -1288,10 +1332,10 @@ impl CefDictionaryValue {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -1301,7 +1345,8 @@ impl CefDictionaryValue {
   // functions if this function returns false (0).
   //
   pub fn is_valid(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1315,7 +1360,8 @@ impl CefDictionaryValue {
   // Returns true (1) if this object is currently owned by another object.
   //
   pub fn is_owned(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1330,7 +1376,8 @@ impl CefDictionaryValue {
   // expose read-only objects.
   //
   pub fn is_read_only(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1346,7 +1393,8 @@ impl CefDictionaryValue {
   // object and vice-versa.
   //
   pub fn is_same(&self, that: interfaces::CefDictionaryValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1362,7 +1410,8 @@ impl CefDictionaryValue {
   // underlying value but are not necessarily the same object.
   //
   pub fn is_equal(&self, that: interfaces::CefDictionaryValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1379,7 +1428,8 @@ impl CefDictionaryValue {
   //
   pub fn copy(&self,
       exclude_empty_children: libc::c_int) -> interfaces::CefDictionaryValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1394,7 +1444,8 @@ impl CefDictionaryValue {
   // Returns the number of values.
   //
   pub fn get_size(&self) -> libc::size_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1408,7 +1459,8 @@ impl CefDictionaryValue {
   // Removes all values. Returns true (1) on success.
   //
   pub fn clear(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1422,7 +1474,8 @@ impl CefDictionaryValue {
   // Returns true (1) if the current dictionary has a value for the given key.
   //
   pub fn has_key(&self, key: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1437,7 +1490,8 @@ impl CefDictionaryValue {
   // Reads all keys for this dictionary into the specified vector.
   //
   pub fn get_keys(&self, keys: Vec<String>) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1453,7 +1507,8 @@ impl CefDictionaryValue {
   // removed successfully.
   //
   pub fn remove(&self, key: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1468,7 +1523,8 @@ impl CefDictionaryValue {
   // Returns the value type for the specified key.
   //
   pub fn get_type(&self, key: &[u16]) -> interfaces::CefValueType {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1487,7 +1543,8 @@ impl CefDictionaryValue {
   // this object.
   //
   pub fn get_value(&self, key: &[u16]) -> interfaces::CefValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1502,7 +1559,8 @@ impl CefDictionaryValue {
   // Returns the value at the specified key as type bool.
   //
   pub fn get_bool(&self, key: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1517,7 +1575,8 @@ impl CefDictionaryValue {
   // Returns the value at the specified key as type int.
   //
   pub fn get_int(&self, key: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1532,7 +1591,8 @@ impl CefDictionaryValue {
   // Returns the value at the specified key as type double.
   //
   pub fn get_double(&self, key: &[u16]) -> libc::c_double {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1548,7 +1608,8 @@ impl CefDictionaryValue {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_string(&self, key: &[u16]) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1564,7 +1625,8 @@ impl CefDictionaryValue {
   // will reference existing data.
   //
   pub fn get_binary(&self, key: &[u16]) -> interfaces::CefBinaryValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1581,7 +1643,8 @@ impl CefDictionaryValue {
   // modify this object.
   //
   pub fn get_dictionary(&self, key: &[u16]) -> interfaces::CefDictionaryValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1598,7 +1661,8 @@ impl CefDictionaryValue {
   // this object.
   //
   pub fn get_list(&self, key: &[u16]) -> interfaces::CefListValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1619,7 +1683,8 @@ impl CefDictionaryValue {
   //
   pub fn set_value(&self, key: &[u16],
       value: interfaces::CefValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1636,7 +1701,8 @@ impl CefDictionaryValue {
   // value was set successfully.
   //
   pub fn set_null(&self, key: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1652,7 +1718,8 @@ impl CefDictionaryValue {
   // value was set successfully.
   //
   pub fn set_bool(&self, key: &[u16], value: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1669,7 +1736,8 @@ impl CefDictionaryValue {
   // value was set successfully.
   //
   pub fn set_int(&self, key: &[u16], value: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1686,7 +1754,8 @@ impl CefDictionaryValue {
   // value was set successfully.
   //
   pub fn set_double(&self, key: &[u16], value: libc::c_double) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1703,7 +1772,8 @@ impl CefDictionaryValue {
   // value was set successfully.
   //
   pub fn set_string(&self, key: &[u16], value: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1724,7 +1794,8 @@ impl CefDictionaryValue {
   //
   pub fn set_binary(&self, key: &[u16],
       value: interfaces::CefBinaryValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1745,7 +1816,8 @@ impl CefDictionaryValue {
   //
   pub fn set_dictionary(&self, key: &[u16],
       value: interfaces::CefDictionaryValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1766,7 +1838,8 @@ impl CefDictionaryValue {
   //
   pub fn set_list(&self, key: &[u16],
       value: interfaces::CefListValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -1806,7 +1879,8 @@ impl CefWrap<*mut cef_dictionary_value_t> for Option<CefDictionaryValue> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_dictionary_value_t) -> Option<CefDictionaryValue> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefDictionaryValue::from_c_object_addref(c_object))
@@ -2038,13 +2112,13 @@ pub struct _cef_list_value_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_list_value_t = _cef_list_value_t;
 
@@ -2059,7 +2133,8 @@ pub struct CefListValue {
 impl Clone for CefListValue {
   fn clone(&self) -> CefListValue{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefListValue {
@@ -2072,7 +2147,8 @@ impl Clone for CefListValue {
 impl Drop for CefListValue {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -2087,7 +2163,8 @@ impl CefListValue {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_list_value_t) -> CefListValue {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefListValue {
@@ -2101,7 +2178,8 @@ impl CefListValue {
 
   pub fn c_object_addrefed(&self) -> *mut cef_list_value_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -2109,10 +2187,10 @@ impl CefListValue {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -2122,7 +2200,8 @@ impl CefListValue {
   // functions if this function returns false (0).
   //
   pub fn is_valid(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2136,7 +2215,8 @@ impl CefListValue {
   // Returns true (1) if this object is currently owned by another object.
   //
   pub fn is_owned(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2151,7 +2231,8 @@ impl CefListValue {
   // expose read-only objects.
   //
   pub fn is_read_only(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2167,7 +2248,8 @@ impl CefListValue {
   // object and vice-versa.
   //
   pub fn is_same(&self, that: interfaces::CefListValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2183,7 +2265,8 @@ impl CefListValue {
   // underlying value but are not necessarily the same object.
   //
   pub fn is_equal(&self, that: interfaces::CefListValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2198,7 +2281,8 @@ impl CefListValue {
   // Returns a writable copy of this object.
   //
   pub fn copy(&self) -> interfaces::CefListValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2213,7 +2297,8 @@ impl CefListValue {
   // value slots will default to type null. Returns true (1) on success.
   //
   pub fn set_size(&self, size: libc::size_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2228,7 +2313,8 @@ impl CefListValue {
   // Returns the number of values.
   //
   pub fn get_size(&self) -> libc::size_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2242,7 +2328,8 @@ impl CefListValue {
   // Removes all values. Returns true (1) on success.
   //
   pub fn clear(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2256,7 +2343,8 @@ impl CefListValue {
   // Removes the value at the specified index.
   //
   pub fn remove(&self, index: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2271,7 +2359,8 @@ impl CefListValue {
   // Returns the value type at the specified index.
   //
   pub fn get_type(&self, index: libc::c_int) -> interfaces::CefValueType {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2290,7 +2379,8 @@ impl CefListValue {
   // will modify this object.
   //
   pub fn get_value(&self, index: libc::c_int) -> interfaces::CefValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2305,7 +2395,8 @@ impl CefListValue {
   // Returns the value at the specified index as type bool.
   //
   pub fn get_bool(&self, index: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2320,7 +2411,8 @@ impl CefListValue {
   // Returns the value at the specified index as type int.
   //
   pub fn get_int(&self, index: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2335,7 +2427,8 @@ impl CefListValue {
   // Returns the value at the specified index as type double.
   //
   pub fn get_double(&self, index: libc::c_int) -> libc::c_double {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2351,7 +2444,8 @@ impl CefListValue {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_string(&self, index: libc::c_int) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2367,7 +2461,8 @@ impl CefListValue {
   // will reference existing data.
   //
   pub fn get_binary(&self, index: libc::c_int) -> interfaces::CefBinaryValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2385,7 +2480,8 @@ impl CefListValue {
   //
   pub fn get_dictionary(&self,
       index: libc::c_int) -> interfaces::CefDictionaryValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2402,7 +2498,8 @@ impl CefListValue {
   // this object.
   //
   pub fn get_list(&self, index: libc::c_int) -> interfaces::CefListValue {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2423,7 +2520,8 @@ impl CefListValue {
   //
   pub fn set_value(&self, index: libc::c_int,
       value: interfaces::CefValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2440,7 +2538,8 @@ impl CefListValue {
   // value was set successfully.
   //
   pub fn set_null(&self, index: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2457,7 +2556,8 @@ impl CefListValue {
   //
   pub fn set_bool(&self, index: libc::c_int,
       value: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2474,7 +2574,8 @@ impl CefListValue {
   // value was set successfully.
   //
   pub fn set_int(&self, index: libc::c_int, value: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2492,7 +2593,8 @@ impl CefListValue {
   //
   pub fn set_double(&self, index: libc::c_int,
       value: libc::c_double) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2509,7 +2611,8 @@ impl CefListValue {
   // the value was set successfully.
   //
   pub fn set_string(&self, index: libc::c_int, value: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2530,7 +2633,8 @@ impl CefListValue {
   //
   pub fn set_binary(&self, index: libc::c_int,
       value: interfaces::CefBinaryValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2551,7 +2655,8 @@ impl CefListValue {
   //
   pub fn set_dictionary(&self, index: libc::c_int,
       value: interfaces::CefDictionaryValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2572,7 +2677,8 @@ impl CefListValue {
   //
   pub fn set_list(&self, index: libc::c_int,
       value: interfaces::CefListValue) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -2612,7 +2718,8 @@ impl CefWrap<*mut cef_list_value_t> for Option<CefListValue> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_list_value_t) -> Option<CefListValue> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefListValue::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_web_plugin.rs b/ports/cef/interfaces/cef_web_plugin.rs
index 6d6bd805246..94019e77ef5 100644
--- a/ports/cef/interfaces/cef_web_plugin.rs
+++ b/ports/cef/interfaces/cef_web_plugin.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -86,13 +87,13 @@ pub struct _cef_web_plugin_info_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_web_plugin_info_t = _cef_web_plugin_info_t;
 
@@ -107,7 +108,8 @@ pub struct CefWebPluginInfo {
 impl Clone for CefWebPluginInfo {
   fn clone(&self) -> CefWebPluginInfo{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefWebPluginInfo {
@@ -120,7 +122,8 @@ impl Clone for CefWebPluginInfo {
 impl Drop for CefWebPluginInfo {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -135,7 +138,8 @@ impl CefWebPluginInfo {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_web_plugin_info_t) -> CefWebPluginInfo {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefWebPluginInfo {
@@ -149,7 +153,8 @@ impl CefWebPluginInfo {
 
   pub fn c_object_addrefed(&self) -> *mut cef_web_plugin_info_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -157,10 +162,10 @@ impl CefWebPluginInfo {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -168,7 +173,8 @@ impl CefWebPluginInfo {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -183,7 +189,8 @@ impl CefWebPluginInfo {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_path(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -198,7 +205,8 @@ impl CefWebPluginInfo {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_version(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -213,7 +221,8 @@ impl CefWebPluginInfo {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_description(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -240,7 +249,8 @@ impl CefWrap<*mut cef_web_plugin_info_t> for Option<CefWebPluginInfo> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_web_plugin_info_t) -> Option<CefWebPluginInfo> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefWebPluginInfo::from_c_object_addref(c_object))
@@ -273,13 +283,13 @@ pub struct _cef_web_plugin_info_visitor_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_web_plugin_info_visitor_t = _cef_web_plugin_info_visitor_t;
 
@@ -295,7 +305,8 @@ pub struct CefWebPluginInfoVisitor {
 impl Clone for CefWebPluginInfoVisitor {
   fn clone(&self) -> CefWebPluginInfoVisitor{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefWebPluginInfoVisitor {
@@ -308,7 +319,8 @@ impl Clone for CefWebPluginInfoVisitor {
 impl Drop for CefWebPluginInfoVisitor {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -323,7 +335,8 @@ impl CefWebPluginInfoVisitor {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_web_plugin_info_visitor_t) -> CefWebPluginInfoVisitor {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefWebPluginInfoVisitor {
@@ -337,7 +350,8 @@ impl CefWebPluginInfoVisitor {
 
   pub fn c_object_addrefed(&self) -> *mut cef_web_plugin_info_visitor_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -345,10 +359,10 @@ impl CefWebPluginInfoVisitor {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -359,7 +373,8 @@ impl CefWebPluginInfoVisitor {
   //
   pub fn visit(&self, info: interfaces::CefWebPluginInfo, count: libc::c_int,
       total: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -389,7 +404,8 @@ impl CefWrap<*mut cef_web_plugin_info_visitor_t> for Option<CefWebPluginInfoVisi
     }
   }
   unsafe fn to_rust(c_object: *mut cef_web_plugin_info_visitor_t) -> Option<CefWebPluginInfoVisitor> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefWebPluginInfoVisitor::from_c_object_addref(c_object))
@@ -421,13 +437,13 @@ pub struct _cef_web_plugin_unstable_callback_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_web_plugin_unstable_callback_t = _cef_web_plugin_unstable_callback_t;
 
@@ -443,7 +459,8 @@ pub struct CefWebPluginUnstableCallback {
 impl Clone for CefWebPluginUnstableCallback {
   fn clone(&self) -> CefWebPluginUnstableCallback{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefWebPluginUnstableCallback {
@@ -456,7 +473,8 @@ impl Clone for CefWebPluginUnstableCallback {
 impl Drop for CefWebPluginUnstableCallback {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -471,7 +489,8 @@ impl CefWebPluginUnstableCallback {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_web_plugin_unstable_callback_t) -> CefWebPluginUnstableCallback {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefWebPluginUnstableCallback {
@@ -485,7 +504,8 @@ impl CefWebPluginUnstableCallback {
 
   pub fn c_object_addrefed(&self) -> *mut cef_web_plugin_unstable_callback_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -493,10 +513,10 @@ impl CefWebPluginUnstableCallback {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -505,7 +525,8 @@ impl CefWebPluginUnstableCallback {
   // 120 seconds.
   //
   pub fn is_unstable(&self, path: &[u16], unstable: libc::c_int) -> () {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -534,7 +555,8 @@ impl CefWrap<*mut cef_web_plugin_unstable_callback_t> for Option<CefWebPluginUns
     }
   }
   unsafe fn to_rust(c_object: *mut cef_web_plugin_unstable_callback_t) -> Option<CefWebPluginUnstableCallback> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefWebPluginUnstableCallback::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_xml_reader.rs b/ports/cef/interfaces/cef_xml_reader.rs
index 02c85f408e3..485ef4c2ee7 100644
--- a/ports/cef/interfaces/cef_xml_reader.rs
+++ b/ports/cef/interfaces/cef_xml_reader.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -277,13 +278,13 @@ pub struct _cef_xml_reader_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_xml_reader_t = _cef_xml_reader_t;
 
@@ -300,7 +301,8 @@ pub struct CefXmlReader {
 impl Clone for CefXmlReader {
   fn clone(&self) -> CefXmlReader{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefXmlReader {
@@ -313,7 +315,8 @@ impl Clone for CefXmlReader {
 impl Drop for CefXmlReader {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -328,7 +331,8 @@ impl CefXmlReader {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_xml_reader_t) -> CefXmlReader {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefXmlReader {
@@ -342,7 +346,8 @@ impl CefXmlReader {
 
   pub fn c_object_addrefed(&self) -> *mut cef_xml_reader_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -350,10 +355,10 @@ impl CefXmlReader {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -362,7 +367,8 @@ impl CefXmlReader {
   // if the cursor position was set successfully.
   //
   pub fn move_to_next_node(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -377,7 +383,8 @@ impl CefXmlReader {
   // occurs on the correct thread.
   //
   pub fn close(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -391,7 +398,8 @@ impl CefXmlReader {
   // Returns true (1) if an error has been reported by the XML parser.
   //
   pub fn has_error(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -406,7 +414,8 @@ impl CefXmlReader {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_error(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -424,7 +433,8 @@ impl CefXmlReader {
   // Returns the node type.
   //
   pub fn get_type(&self) -> types::cef_xml_node_type_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -438,7 +448,8 @@ impl CefXmlReader {
   // Returns the node depth. Depth starts at 0 for the root node.
   //
   pub fn get_depth(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -454,7 +465,8 @@ impl CefXmlReader {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_local_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -470,7 +482,8 @@ impl CefXmlReader {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_prefix(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -486,7 +499,8 @@ impl CefXmlReader {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_qualified_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -502,7 +516,8 @@ impl CefXmlReader {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_namespace_uri(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -518,7 +533,8 @@ impl CefXmlReader {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_base_uri(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -534,7 +550,8 @@ impl CefXmlReader {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_xml_lang(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -549,7 +566,8 @@ impl CefXmlReader {
   // NULL but <a></a> is not.
   //
   pub fn is_empty_element(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -563,7 +581,8 @@ impl CefXmlReader {
   // Returns true (1) if the node has a text value.
   //
   pub fn has_value(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -578,7 +597,8 @@ impl CefXmlReader {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_value(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -592,7 +612,8 @@ impl CefXmlReader {
   // Returns true (1) if the node has attributes.
   //
   pub fn has_attributes(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -606,7 +627,8 @@ impl CefXmlReader {
   // Returns the number of attributes.
   //
   pub fn get_attribute_count(&self) -> libc::size_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -621,7 +643,8 @@ impl CefXmlReader {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_attribute_byindex(&self, index: libc::c_int) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -637,7 +660,8 @@ impl CefXmlReader {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_attribute_byqname(&self, qualifiedName: &[u16]) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -655,7 +679,8 @@ impl CefXmlReader {
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_attribute_bylname(&self, localName: &[u16],
       namespaceURI: &[u16]) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -672,7 +697,8 @@ impl CefXmlReader {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_inner_xml(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -687,7 +713,8 @@ impl CefXmlReader {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_outer_xml(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -701,7 +728,8 @@ impl CefXmlReader {
   // Returns the line number for the current node.
   //
   pub fn get_line_number(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -722,7 +750,8 @@ impl CefXmlReader {
   // true (1) if the cursor position was set successfully.
   //
   pub fn move_to_attribute_byindex(&self, index: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -739,7 +768,8 @@ impl CefXmlReader {
   //
   pub fn move_to_attribute_byqname(&self,
       qualifiedName: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -757,7 +787,8 @@ impl CefXmlReader {
   //
   pub fn move_to_attribute_bylname(&self, localName: &[u16],
       namespaceURI: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -774,7 +805,8 @@ impl CefXmlReader {
   // true (1) if the cursor position was set successfully.
   //
   pub fn move_to_first_attribute(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -789,7 +821,8 @@ impl CefXmlReader {
   // (1) if the cursor position was set successfully.
   //
   pub fn move_to_next_attribute(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -804,7 +837,8 @@ impl CefXmlReader {
   // cursor position was set successfully.
   //
   pub fn move_to_carrying_element(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -847,7 +881,8 @@ impl CefWrap<*mut cef_xml_reader_t> for Option<CefXmlReader> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_xml_reader_t) -> Option<CefXmlReader> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefXmlReader::from_c_object_addref(c_object))
diff --git a/ports/cef/interfaces/cef_zip_reader.rs b/ports/cef/interfaces/cef_zip_reader.rs
index 6eb4cd45d8b..39b104ae8cf 100644
--- a/ports/cef/interfaces/cef_zip_reader.rs
+++ b/ports/cef/interfaces/cef_zip_reader.rs
@@ -43,6 +43,7 @@ use wrappers::CefWrap;
 
 use libc;
 use std::collections::HashMap;
+use std::mem;
 use std::ptr;
 
 //
@@ -140,13 +141,13 @@ pub struct _cef_zip_reader_t {
   //
   // The reference count. This will only be present for Rust instances!
   //
-  pub ref_count: usize,
+  pub ref_count: u32,
 
   //
   // Extra data. This will only be present for Rust instances!
   //
   pub extra: u8,
-} 
+}
 
 pub type cef_zip_reader_t = _cef_zip_reader_t;
 
@@ -163,7 +164,8 @@ pub struct CefZipReader {
 impl Clone for CefZipReader {
   fn clone(&self) -> CefZipReader{
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.add_ref.unwrap())(&mut (*self.c_object).base);
       }
       CefZipReader {
@@ -176,7 +178,8 @@ impl Clone for CefZipReader {
 impl Drop for CefZipReader {
   fn drop(&mut self) {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         ((*self.c_object).base.release.unwrap())(&mut (*self.c_object).base);
       }
     }
@@ -191,7 +194,8 @@ impl CefZipReader {
   }
 
   pub unsafe fn from_c_object_addref(c_object: *mut cef_zip_reader_t) -> CefZipReader {
-    if !c_object.is_null() {
+    if !c_object.is_null() &&
+        c_object as usize != mem::POST_DROP_USIZE {
       ((*c_object).base.add_ref.unwrap())(&mut (*c_object).base);
     }
     CefZipReader {
@@ -205,7 +209,8 @@ impl CefZipReader {
 
   pub fn c_object_addrefed(&self) -> *mut cef_zip_reader_t {
     unsafe {
-      if !self.c_object.is_null() {
+      if !self.c_object.is_null() &&
+          self.c_object as usize != mem::POST_DROP_USIZE {
         eutil::add_ref(self.c_object as *mut types::cef_base_t);
       }
       self.c_object
@@ -213,10 +218,10 @@ impl CefZipReader {
   }
 
   pub fn is_null_cef_object(&self) -> bool {
-    self.c_object.is_null()
+    self.c_object.is_null() || self.c_object as usize == mem::POST_DROP_USIZE
   }
   pub fn is_not_null_cef_object(&self) -> bool {
-    !self.c_object.is_null()
+    !self.c_object.is_null() && self.c_object as usize != mem::POST_DROP_USIZE
   }
 
   //
@@ -224,7 +229,8 @@ impl CefZipReader {
   // cursor position was set successfully.
   //
   pub fn move_to_first_file(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -239,7 +245,8 @@ impl CefZipReader {
   // cursor position was set successfully.
   //
   pub fn move_to_next_file(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -256,7 +263,8 @@ impl CefZipReader {
   //
   pub fn move_to_file(&self, fileName: &[u16],
       caseSensitive: libc::c_int) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -273,7 +281,8 @@ impl CefZipReader {
   // occurs on the correct thread.
   //
   pub fn close(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -291,7 +300,8 @@ impl CefZipReader {
   //
   // The resulting string must be freed by calling cef_string_userfree_free().
   pub fn get_file_name(&self) -> String {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -305,7 +315,8 @@ impl CefZipReader {
   // Returns the uncompressed size of the file.
   //
   pub fn get_file_size(&self) -> i64 {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -319,7 +330,8 @@ impl CefZipReader {
   // Returns the last modified timestamp for the file.
   //
   pub fn get_file_last_modified(&self) -> libc::time_t {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -334,7 +346,8 @@ impl CefZipReader {
   // optionally be specified.
   //
   pub fn open_file(&self, password: &[u16]) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -349,7 +362,8 @@ impl CefZipReader {
   // Closes the file.
   //
   pub fn close_file(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -365,7 +379,8 @@ impl CefZipReader {
   //
   pub fn read_file(&self, buffer: &mut (),
       bufferSize: libc::size_t) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -381,7 +396,8 @@ impl CefZipReader {
   // Returns the current offset in the uncompressed file contents.
   //
   pub fn tell(&self) -> i64 {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -395,7 +411,8 @@ impl CefZipReader {
   // Returns true (1) if at end of the file contents.
   //
   pub fn eof(&self) -> libc::c_int {
-    if self.c_object.is_null() {
+    if self.c_object.is_null() ||
+       self.c_object as usize == mem::POST_DROP_USIZE {
       panic!("called a CEF method on a null object")
     }
     unsafe {
@@ -435,7 +452,8 @@ impl CefWrap<*mut cef_zip_reader_t> for Option<CefZipReader> {
     }
   }
   unsafe fn to_rust(c_object: *mut cef_zip_reader_t) -> Option<CefZipReader> {
-    if c_object.is_null() {
+    if c_object.is_null() &&
+       c_object as usize != mem::POST_DROP_USIZE {
       None
     } else {
       Some(CefZipReader::from_c_object_addref(c_object))
diff --git a/ports/cef/lib.rs b/ports/cef/lib.rs
index 2f6718a1dea..ae9209022ef 100644
--- a/ports/cef/lib.rs
+++ b/ports/cef/lib.rs
@@ -13,7 +13,7 @@
 #![feature(collections)]
 #![feature(negate_unsigned)]
 #![feature(unicode)]
-
+#![feature(unsafe_no_drop_flag, filling_drop)]
 #![allow(non_camel_case_types)]
 
 #![plugin(plugins)]
diff --git a/ports/cef/macros.rs b/ports/cef/macros.rs
index 605b92da672..f498769e6c9 100644
--- a/ports/cef/macros.rs
+++ b/ports/cef/macros.rs
@@ -66,7 +66,7 @@ macro_rules! full_cef_class_impl(
                     // Calculate the offset of the reference count. This is the size of the
                     // structure.
                     let null: *const $c_interface_name = ::std::ptr::null();
-                    let offset: *const usize = &(*null).ref_count;
+                    let offset: *const u32 = &(*null).ref_count;
                     let size = (offset as ::libc::size_t) - (null as ::libc::size_t);
                     $interface_name::from_c_object_addref(
                         ::eutil::create_cef_object::<$c_interface_name,$class_name>(size))