diff --git a/Makefile.in b/Makefile.in
index c2a2537a07b..8ad50a95772 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -30,7 +30,7 @@ B := $(CFG_BUILD_DIR)
 MKFILE_DEPS := $(CFG_BUILD_HOME)config.stamp $(call rwildcard,$(S)mk/,*)
 
 CFG_GCCISH_CFLAGS += -DRUST_DEBUG
-CFG_RUSTC_FLAGS += -D unused-imports
+CFG_RUSTC_FLAGS += -D unused-imports -D unused-variable
 
 ifdef CFG_DISABLE_OPTIMIZE
   $(info cfg: disabling rustc optimization (CFG_DISABLE_OPTIMIZE))
diff --git a/src/components/embedding/browser.rs b/src/components/embedding/browser.rs
index 6eda47da1b2..9f23d10464c 100644
--- a/src/components/embedding/browser.rs
+++ b/src/components/embedding/browser.rs
@@ -8,20 +8,22 @@ use std::mem;
 use types::{cef_browser_settings_t, cef_browser_t, cef_client_t, cef_request_context_t, cef_string_t, cef_window_info_t};
 
 #[no_mangle]
-pub extern "C" fn cef_browser_host_create_browser(windowInfo: *cef_window_info_t,
-                                            client: *mut cef_client_t,
-                                            url: *cef_string_t,
-                                            settings: *cef_browser_settings_t,
-                                            request_context: *mut cef_request_context_t) -> c_int {
+pub extern "C" fn cef_browser_host_create_browser(_windowInfo: *cef_window_info_t,
+                                                  _client: *mut cef_client_t,
+                                                  _url: *cef_string_t,
+                                                  _settings: *cef_browser_settings_t,
+                                                  _request_context: *mut cef_request_context_t)
+                                                  -> c_int {
     0
 }
 
 #[no_mangle]
-pub extern "C" fn cef_browser_host_create_browser_sync(windowInfo: *cef_window_info_t,
-                                            client: *mut cef_client_t,
-                                            url: *cef_string_t,
-                                            settings: *cef_browser_settings_t,
-                                            request_context: *mut cef_request_context_t) -> *mut cef_browser_t {
+pub extern "C" fn cef_browser_host_create_browser_sync(_windowInfo: *cef_window_info_t,
+                                                       _client: *mut cef_client_t,
+                                                       _url: *cef_string_t,
+                                                       _settings: *cef_browser_settings_t,
+                                                       _request_context: *mut cef_request_context_t)
+                                                       -> *mut cef_browser_t {
     unsafe {
         let browser = calloc(1, mem::size_of::<cef_browser_t>() as size_t) as *mut cef_browser_t;
         browser
diff --git a/src/components/embedding/core.rs b/src/components/embedding/core.rs
index f81d4b14e38..0bb0995d9fe 100644
--- a/src/components/embedding/core.rs
+++ b/src/components/embedding/core.rs
@@ -15,8 +15,11 @@ use types::{cef_app_t, cef_main_args_t, cef_settings_t};
 
 
 #[no_mangle]
-pub extern "C" fn cef_initialize(args: *cef_main_args_t, settings: *mut cef_settings_t,
-                      application: *mut cef_app_t, windows_sandbox_info: *c_void) -> c_int {
+pub extern "C" fn cef_initialize(args: *cef_main_args_t,
+                                 _settings: *mut cef_settings_t,
+                                 application: *mut cef_app_t,
+                                 _windows_sandbox_info: *c_void)
+                                 -> c_int {
     if args.is_null() {
         return 0;
     }
@@ -71,6 +74,9 @@ pub extern "C" fn cef_quit_message_loop() {
 }
 
 #[no_mangle]
-pub extern "C" fn cef_execute_process(args: *cef_main_args_t, app: *mut cef_app_t, windows_sandbox_info: *mut c_void) -> c_int {
+pub extern "C" fn cef_execute_process(_args: *cef_main_args_t,
+                                      _app: *mut cef_app_t,
+                                      _windows_sandbox_info: *mut c_void)
+                                      -> c_int {
    -1
 }
diff --git a/src/components/embedding/task.rs b/src/components/embedding/task.rs
index 825a75f92bc..6992149d1b9 100644
--- a/src/components/embedding/task.rs
+++ b/src/components/embedding/task.rs
@@ -7,6 +7,6 @@ use types::cef_thread_id_t;
 
 //FIXME: this should check the current servo task I guess?
 #[no_mangle]
-pub extern "C" fn cef_currently_on(tid: cef_thread_id_t) -> c_int {
+pub extern "C" fn cef_currently_on(_tid: cef_thread_id_t) -> c_int {
     1
 }
diff --git a/src/components/embedding/urlrequest.rs b/src/components/embedding/urlrequest.rs
index 46857e3217c..e55546325d0 100644
--- a/src/components/embedding/urlrequest.rs
+++ b/src/components/embedding/urlrequest.rs
@@ -7,6 +7,8 @@ use types::{cef_request_t, cef_urlrequest_client_t, cef_urlrequest_t};
 
 
 #[no_mangle]
-pub extern "C" fn cef_urlrequest_create(request: *mut cef_request_t, client: *mut cef_urlrequest_client_t) -> *mut cef_urlrequest_t {
+pub extern "C" fn cef_urlrequest_create(_request: *mut cef_request_t,
+                                        _client: *mut cef_urlrequest_client_t)
+                                        -> *mut cef_urlrequest_t {
     0 as *mut cef_urlrequest_t
 }