diff --git a/components/net/Cargo.toml b/components/net/Cargo.toml
index f8c9a6bb5ea..385f81da21e 100644
--- a/components/net/Cargo.toml
+++ b/components/net/Cargo.toml
@@ -43,6 +43,7 @@ openssl = "0.7.6"
 rustc-serialize = "0.3"
 threadpool = "1.0"
 time = "0.1.17"
+unicase = "1.4.0"
 url = {version = "0.5.7", features = ["heap_size"]}
 uuid = { version = "0.2", features = ["v4"] }
 websocket = "0.16.1"
diff --git a/components/net/fetch/methods.rs b/components/net/fetch/methods.rs
index 0980bfee301..a9a8a3969f8 100644
--- a/components/net/fetch/methods.rs
+++ b/components/net/fetch/methods.rs
@@ -5,12 +5,12 @@
 use data_loader::decode;
 use fetch::cors_cache::{BasicCORSCache, CORSCache, CacheRequestDetails};
 use http_loader::{NetworkHttpRequestFactory, create_http_connector, obtain_response};
-use hyper::header::{Accept, CacheControl, IfMatch, IfRange, IfUnmodifiedSince, Location};
-use hyper::header::{AcceptLanguage, ContentLength, ContentLanguage, HeaderView, Pragma};
-use hyper::header::{AccessControlAllowCredentials, AccessControlAllowOrigin};
-use hyper::header::{Authorization, Basic, CacheDirective, ContentEncoding, Encoding};
-use hyper::header::{ContentType, Headers, IfModifiedSince, IfNoneMatch};
-use hyper::header::{QualityItem, q, qitem, Referer as RefererHeader, UserAgent};
+use hyper::header::{Accept, AcceptLanguage, Authorization, AccessControlAllowCredentials};
+use hyper::header::{AccessControlAllowOrigin, AccessControlAllowHeaders, AccessControlAllowMethods};
+use hyper::header::{AccessControlRequestHeaders, AccessControlMaxAge, AccessControlRequestMethod, Basic};
+use hyper::header::{CacheControl, CacheDirective, ContentEncoding, ContentLength, ContentLanguage, ContentType};
+use hyper::header::{Encoding, HeaderView, Headers, IfMatch, IfRange, IfUnmodifiedSince, IfModifiedSince};
+use hyper::header::{IfNoneMatch, Pragma, Location, QualityItem, Referer as RefererHeader, UserAgent, q, qitem};
 use hyper::method::Method;
 use hyper::mime::{Attr, Mime, SubLevel, TopLevel, Value};
 use hyper::status::StatusCode;
@@ -20,9 +20,12 @@ use net_traits::request::{RedirectMode, Referer, Request, RequestMode, ResponseT
 use net_traits::response::{HttpsState, TerminationReason};
 use net_traits::response::{Response, ResponseBody, ResponseType};
 use resource_thread::CancellationListener;
+use std::collections::HashSet;
 use std::io::Read;
+use std::iter::FromIterator;
 use std::rc::Rc;
 use std::thread;
+use unicase::UniCase;
 use url::idna::domain_to_ascii;
 use url::{Origin as UrlOrigin, OpaqueOrigin, Url, UrlParser, whatwg_scheme_type_mapper};
 use util::thread::spawn_named;
@@ -210,7 +213,7 @@ fn main_fetch(request: Rc<Request>, cors_flag: bool, recursive_flag: bool) -> Re
         let internal_response = if response.is_network_error() {
             &network_error_res
         } else {
-            response.get_actual_response()
+            response.actual_response()
         };
 
         // Step 13
@@ -245,7 +248,7 @@ fn main_fetch(request: Rc<Request>, cors_flag: bool, recursive_flag: bool) -> Re
 
     // Step 16
     if request.synchronous {
-        response.get_actual_response().wait_until_done();
+        response.actual_response().wait_until_done();
         return response;
     }
 
@@ -263,7 +266,7 @@ fn main_fetch(request: Rc<Request>, cors_flag: bool, recursive_flag: bool) -> Re
         let internal_response = if response.is_network_error() {
             &network_error_res
         } else {
-            response.get_actual_response()
+            response.actual_response()
         };
 
         // Step 18
@@ -367,7 +370,7 @@ fn http_fetch(request: Rc<Request>,
             }
 
             // Substep 4
-            let actual_response = res.get_actual_response();
+            let actual_response = res.actual_response();
             if actual_response.url_list.borrow().is_empty() {
                 *actual_response.url_list.borrow_mut() = request.url_list.borrow().clone();
             }
@@ -392,7 +395,7 @@ fn http_fetch(request: Rc<Request>,
             }, request.method.borrow().clone());
 
             let method_mismatch = !method_cache_match && (!is_simple_method(&request.method.borrow()) ||
-                request.use_cors_preflight);
+                                                          request.use_cors_preflight);
             let header_mismatch = request.headers.borrow().iter().any(|view|
                 !cache.match_header(CacheRequestDetails {
                     origin: origin.clone(),
@@ -403,7 +406,7 @@ fn http_fetch(request: Rc<Request>,
 
             // Sub-substep 1
             if method_mismatch || header_mismatch {
-                let preflight_result = preflight_fetch(request.clone());
+                let preflight_result = cors_preflight_fetch(request.clone(), Some(cache));
                 // Sub-substep 2
                 if preflight_result.response_type == ResponseType::Error {
                     return Response::network_error();
@@ -417,8 +420,7 @@ fn http_fetch(request: Rc<Request>,
         // Substep 3
         let credentials = match request.credentials_mode {
             CredentialsMode::Include => true,
-            CredentialsMode::CredentialsSameOrigin if
-                request.response_tainting.get() == ResponseTainting::Basic
+            CredentialsMode::CredentialsSameOrigin if request.response_tainting.get() == ResponseTainting::Basic
                 => true,
             _ => false
         };
@@ -439,7 +441,7 @@ fn http_fetch(request: Rc<Request>,
     let mut response = response.unwrap();
 
     // Step 5
-    match response.get_actual_response().status.unwrap() {
+    match response.actual_response().status.unwrap() {
 
         // Code 301, 302, 303, 307, 308
         StatusCode::MovedPermanently | StatusCode::Found | StatusCode::SeeOther |
@@ -520,21 +522,21 @@ fn http_redirect_fetch(request: Rc<Request>,
     assert_eq!(response.return_internal.get(), true);
 
     // Step 3
-    // this step is done early, because querying if Location is available says
+    // this step is done early, because querying if Location exists says
     // if it is None or Some, making it easy to seperate from the retrieval failure case
-    if !response.get_actual_response().headers.has::<Location>() {
+    if !response.actual_response().headers.has::<Location>() {
         return Rc::try_unwrap(response).ok().unwrap();
     }
 
     // Step 2
-    let location = match response.get_actual_response().headers.get::<Location>() {
+    let location = match response.actual_response().headers.get::<Location>() {
         Some(&Location(ref location)) => location.clone(),
         // Step 4
         _ => return Response::network_error()
     };
 
     // Step 5
-    let response_url = response.get_actual_response().url.as_ref().unwrap();
+    let response_url = response.actual_response().url.as_ref().unwrap();
     let location_url = UrlParser::new().base_url(response_url).parse(&*location);
 
     // Step 6
@@ -577,7 +579,7 @@ fn http_redirect_fetch(request: Rc<Request>,
     }
 
     // Step 13
-    let status_code = response.get_actual_response().status.unwrap();
+    let status_code = response.actual_response().status.unwrap();
     if ((status_code == StatusCode::MovedPermanently || status_code == StatusCode::Found) &&
         *request.method.borrow() == Method::Post) ||
         status_code == StatusCode::SeeOther {
@@ -878,11 +880,11 @@ fn http_network_fetch(request: Rc<Request>,
 
         // Substep 2
 
-    // TODO how can I tell if response was retrieved over HTTPS?
+    // TODO Determine if response was retrieved over HTTPS
     // TODO Servo needs to decide what ciphers are to be treated as "deprecated"
     response.https_state = HttpsState::None;
 
-    // TODO how do I read request?
+    // TODO Read request
 
     // Step 5
     // TODO when https://bugzilla.mozilla.org/show_bug.cgi?id=1030660
@@ -927,8 +929,113 @@ fn http_network_fetch(request: Rc<Request>,
 }
 
 /// [CORS preflight fetch](https://fetch.spec.whatwg.org#cors-preflight-fetch)
-fn preflight_fetch(_request: Rc<Request>) -> Response {
-    // TODO: Implement preflight fetch spec
+fn cors_preflight_fetch(request: Rc<Request>, cache: Option<BasicCORSCache>) -> Response {
+    // Step 1
+    let mut preflight = Request::new(request.current_url(), Some(request.origin.borrow().clone()), false);
+    *preflight.method.borrow_mut() = Method::Options;
+    preflight.initiator = request.initiator.clone();
+    preflight.type_ = request.type_.clone();
+    preflight.destination = request.destination.clone();
+    preflight.referer = request.referer.clone();
+
+    // Step 2
+    preflight.headers.borrow_mut().set::<AccessControlRequestMethod>(
+        AccessControlRequestMethod(request.method.borrow().clone()));
+
+    // Step 3, 4
+    let mut value = request.headers.borrow().iter()
+                                            .filter_map(|ref view| if is_simple_header(view) {
+                                                None
+                                            } else {
+                                                Some(UniCase(view.name().to_owned()))
+                                            }).collect::<Vec<UniCase<String>>>();
+    value.sort();
+
+    // Step 5
+    preflight.headers.borrow_mut().set::<AccessControlRequestHeaders>(
+        AccessControlRequestHeaders(value));
+
+    // Step 6
+    let preflight = Rc::new(preflight);
+    let response = http_network_or_cache_fetch(preflight.clone(), false, false);
+
+    // Step 7
+    if cors_check(request.clone(), &response).is_ok() &&
+       response.status.map_or(false, |status| status.is_success()) {
+        // Substep 1
+        let mut methods = if response.headers.has::<AccessControlAllowMethods>() {
+            match response.headers.get::<AccessControlAllowMethods>() {
+                Some(&AccessControlAllowMethods(ref m)) => m.clone(),
+                // Substep 3
+                None => return Response::network_error()
+            }
+        } else {
+            vec![]
+        };
+
+        // Substep 2
+        let header_names = if response.headers.has::<AccessControlAllowHeaders>() {
+            match response.headers.get::<AccessControlAllowHeaders>() {
+                Some(&AccessControlAllowHeaders(ref hn)) => hn.clone(),
+                // Substep 3
+                None => return Response::network_error()
+            }
+        } else {
+            vec![]
+        };
+
+        // Substep 4
+        if methods.is_empty() && request.use_cors_preflight {
+            methods = vec![request.method.borrow().clone()];
+        }
+
+        // Substep 5
+        if methods.iter().all(|method| *method != *request.method.borrow()) &&
+            !is_simple_method(&*request.method.borrow()) {
+            return Response::network_error();
+        }
+
+        // Substep 6
+        let set: HashSet<&UniCase<String>> = HashSet::from_iter(header_names.iter());
+        if request.headers.borrow().iter().any(|ref hv| !set.contains(&UniCase(hv.name().to_owned())) &&
+                                                        !is_simple_header(hv)) {
+            return Response::network_error();
+        }
+
+        // Substep 7, 8
+        let max_age = response.headers.get::<AccessControlMaxAge>().map(|acma| acma.0).unwrap_or(0);
+
+        // TODO: Substep 9 - Need to define what an imposed limit on max-age is
+
+        // Substep 10
+        let mut cache = match cache {
+            Some(c) => c,
+            None => return response
+        };
+
+        // Substep 11, 12
+        for method in &methods {
+            cache.match_method_and_update(CacheRequestDetails {
+                origin: request.origin.borrow().clone(),
+                destination: request.current_url(),
+                credentials: request.credentials_mode == CredentialsMode::Include
+            }, method.clone(), max_age);
+        }
+
+        // Substep 13, 14
+        for header_name in &header_names {
+            cache.match_header_and_update(CacheRequestDetails {
+                origin: request.origin.borrow().clone(),
+                destination: request.current_url(),
+                credentials: request.credentials_mode == CredentialsMode::Include
+            }, &*header_name, max_age);
+        }
+
+        // Substep 15
+        return response;
+    }
+
+    // Step 8
     Response::network_error()
 }
 
@@ -936,7 +1043,6 @@ fn preflight_fetch(_request: Rc<Request>) -> Response {
 fn cors_check(request: Rc<Request>, response: &Response) -> Result<(), ()> {
 
     // Step 1
-    // let headers = request.headers.borrow();
     let origin = response.headers.get::<AccessControlAllowOrigin>().cloned();
 
     // Step 2
@@ -944,18 +1050,18 @@ fn cors_check(request: Rc<Request>, response: &Response) -> Result<(), ()> {
 
     // Step 3
     if request.credentials_mode != CredentialsMode::Include &&
-        origin == AccessControlAllowOrigin::Any {
+       origin == AccessControlAllowOrigin::Any {
         return Ok(());
     }
 
     // Step 4
     let origin = match origin {
         AccessControlAllowOrigin::Value(origin) => origin,
-        // if it's Any or Null at this point, I see nothing to do but return Err(())
+        // if it's Any or Null at this point, there's nothing to do but return Err(())
         _ => return Err(())
     };
 
-    // strings are already utf-8 encoded, so I don't need to re-encode origin for this step
+    // strings are already utf-8 encoded, so there's no need to re-encode origin for this step
     match ascii_serialise_origin(&request.origin.borrow()) {
         Ok(request_origin) => {
             if request_origin != origin {
diff --git a/components/net/lib.rs b/components/net/lib.rs
index 2b008a89a32..1926bee5085 100644
--- a/components/net/lib.rs
+++ b/components/net/lib.rs
@@ -27,6 +27,7 @@ extern crate openssl;
 extern crate rustc_serialize;
 extern crate threadpool;
 extern crate time;
+extern crate unicase;
 extern crate url;
 extern crate util;
 extern crate uuid;
@@ -47,7 +48,7 @@ pub mod resource_thread;
 pub mod storage_thread;
 pub mod websocket_loader;
 
-/// An implementation of the [Fetch spec](https://fetch.spec.whatwg.org/)
+/// An implementation of the [Fetch specification](https://fetch.spec.whatwg.org/)
 pub mod fetch {
     pub mod cors_cache;
     pub mod methods;
diff --git a/components/net_traits/response.rs b/components/net_traits/response.rs
index 9e6cedd2765..1c1796df52a 100644
--- a/components/net_traits/response.rs
+++ b/components/net_traits/response.rs
@@ -144,7 +144,7 @@ impl Response {
         }
     }
 
-    pub fn get_actual_response(&self) -> &Response {
+    pub fn actual_response(&self) -> &Response {
         if self.return_internal.get() && self.internal_response.is_some() {
             &**self.internal_response.as_ref().unwrap()
         } else {
diff --git a/components/servo/Cargo.lock b/components/servo/Cargo.lock
index 122dca34ba6..ba51bf7418e 100644
--- a/components/servo/Cargo.lock
+++ b/components/servo/Cargo.lock
@@ -918,7 +918,7 @@ dependencies = [
  "time 0.1.34 (registry+https://github.com/rust-lang/crates.io-index)",
  "traitobject 0.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "typeable 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "unicase 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicase 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1294,6 +1294,7 @@ dependencies = [
  "rustc-serialize 0.3.16 (registry+https://github.com/rust-lang/crates.io-index)",
  "threadpool 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "time 0.1.34 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicase 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "util 0.0.1",
  "uuid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1327,7 +1328,7 @@ dependencies = [
  "net_traits 0.0.1",
  "plugins 0.0.1",
  "time 0.1.34 (registry+https://github.com/rust-lang/crates.io-index)",
- "unicase 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicase 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "util 0.0.1",
 ]
@@ -1737,7 +1738,7 @@ dependencies = [
  "string_cache 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "style 0.0.1",
  "time 0.1.34 (registry+https://github.com/rust-lang/crates.io-index)",
- "unicase 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicase 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "util 0.0.1",
  "uuid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2102,8 +2103,11 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "unicase"
-version = "1.0.1"
+version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "rustc_version 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
+]
 
 [[package]]
 name = "unicode-bidi"
@@ -2355,7 +2359,7 @@ dependencies = [
  "openssl 0.7.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.3.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.16 (registry+https://github.com/rust-lang/crates.io-index)",
- "unicase 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicase 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
diff --git a/ports/cef/Cargo.lock b/ports/cef/Cargo.lock
index 19a76595c6a..44482780143 100644
--- a/ports/cef/Cargo.lock
+++ b/ports/cef/Cargo.lock
@@ -837,7 +837,7 @@ dependencies = [
  "time 0.1.34 (registry+https://github.com/rust-lang/crates.io-index)",
  "traitobject 0.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "typeable 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "unicase 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicase 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1206,6 +1206,7 @@ dependencies = [
  "rustc-serialize 0.3.16 (registry+https://github.com/rust-lang/crates.io-index)",
  "threadpool 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "time 0.1.34 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicase 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "util 0.0.1",
  "uuid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1604,7 +1605,7 @@ dependencies = [
  "string_cache 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "style 0.0.1",
  "time 0.1.34 (registry+https://github.com/rust-lang/crates.io-index)",
- "unicase 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicase 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "util 0.0.1",
  "uuid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1981,8 +1982,11 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "unicase"
-version = "1.0.1"
+version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "rustc_version 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
+]
 
 [[package]]
 name = "unicode-bidi"
@@ -2223,7 +2227,7 @@ dependencies = [
  "openssl 0.7.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.3.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.16 (registry+https://github.com/rust-lang/crates.io-index)",
- "unicase 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicase 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
diff --git a/ports/gonk/Cargo.lock b/ports/gonk/Cargo.lock
index b741ead8af2..49b5dee5f4a 100644
--- a/ports/gonk/Cargo.lock
+++ b/ports/gonk/Cargo.lock
@@ -819,7 +819,7 @@ dependencies = [
  "time 0.1.34 (registry+https://github.com/rust-lang/crates.io-index)",
  "traitobject 0.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "typeable 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "unicase 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicase 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1188,6 +1188,7 @@ dependencies = [
  "rustc-serialize 0.3.16 (registry+https://github.com/rust-lang/crates.io-index)",
  "threadpool 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "time 0.1.34 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicase 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "util 0.0.1",
  "uuid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1586,7 +1587,7 @@ dependencies = [
  "string_cache 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "style 0.0.1",
  "time 0.1.34 (registry+https://github.com/rust-lang/crates.io-index)",
- "unicase 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicase 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "util 0.0.1",
  "uuid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1961,8 +1962,11 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "unicase"
-version = "1.0.1"
+version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "rustc_version 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
+]
 
 [[package]]
 name = "unicode-bidi"
@@ -2173,7 +2177,7 @@ dependencies = [
  "openssl 0.7.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.3.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.16 (registry+https://github.com/rust-lang/crates.io-index)",
- "unicase 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicase 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 0.5.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
diff --git a/tests/unit/net/fetch.rs b/tests/unit/net/fetch.rs
index 4b6eff5da69..b2353d33113 100644
--- a/tests/unit/net/fetch.rs
+++ b/tests/unit/net/fetch.rs
@@ -2,7 +2,8 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use hyper::header::{AccessControlAllowHeaders, AccessControlAllowOrigin};
+use hyper::header::{AccessControlAllowCredentials, AccessControlAllowHeaders, AccessControlAllowOrigin};
+use hyper::header::{AccessControlAllowMethods, AccessControlRequestHeaders, AccessControlRequestMethod};
 use hyper::header::{CacheControl, ContentLanguage, ContentType, Expires, LastModified};
 use hyper::header::{Headers, HttpDate, Location, SetCookie, Pragma};
 use hyper::method::Method;
@@ -16,6 +17,7 @@ use net_traits::AsyncFetchListener;
 use net_traits::request::{Origin, RedirectMode, Referer, Request, RequestMode};
 use net_traits::response::{CacheState, Response, ResponseBody, ResponseType};
 use std::rc::Rc;
+use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::mpsc::{Sender, channel};
 use std::sync::{Arc, Mutex};
 use time::{self, Duration};
@@ -136,6 +138,74 @@ fn test_fetch_data() {
     }
 }
 
+#[test]
+fn test_cors_preflight_fetch() {
+    static ACK: &'static [u8] = b"ACK";
+    let state = Arc::new(AtomicUsize::new(0));
+    let handler = move |request: HyperRequest, mut response: HyperResponse| {
+        if request.method == Method::Options && state.clone().fetch_add(1, Ordering::SeqCst) == 0 {
+            assert!(request.headers.has::<AccessControlRequestMethod>());
+            assert!(request.headers.has::<AccessControlRequestHeaders>());
+            response.headers_mut().set(AccessControlAllowOrigin::Any);
+            response.headers_mut().set(AccessControlAllowCredentials);
+            response.headers_mut().set(AccessControlAllowMethods(vec![Method::Get]));
+        } else {
+            response.headers_mut().set(AccessControlAllowOrigin::Any);
+            response.send(ACK).unwrap();
+        }
+    };
+    let (mut server, url) = make_server(handler);
+
+    let origin = Origin::Origin(UrlOrigin::UID(OpaqueOrigin::new()));
+    let mut request = Request::new(url, Some(origin), false);
+    request.referer = Referer::NoReferer;
+    request.use_cors_preflight = true;
+    request.mode = RequestMode::CORSMode;
+    let wrapped_request = Rc::new(request);
+
+    let fetch_response = fetch(wrapped_request);
+    let _ = server.close();
+
+    assert!(!fetch_response.is_network_error());
+
+    match *fetch_response.body.lock().unwrap() {
+        ResponseBody::Done(ref body) => assert_eq!(&**body, ACK),
+        _ => panic!()
+    };
+}
+
+#[test]
+fn test_cors_preflight_fetch_network_error() {
+    static ACK: &'static [u8] = b"ACK";
+    let state = Arc::new(AtomicUsize::new(0));
+    let handler = move |request: HyperRequest, mut response: HyperResponse| {
+        if request.method == Method::Options && state.clone().fetch_add(1, Ordering::SeqCst) == 0 {
+            assert!(request.headers.has::<AccessControlRequestMethod>());
+            assert!(request.headers.has::<AccessControlRequestHeaders>());
+            response.headers_mut().set(AccessControlAllowOrigin::Any);
+            response.headers_mut().set(AccessControlAllowCredentials);
+            response.headers_mut().set(AccessControlAllowMethods(vec![Method::Get]));
+        } else {
+            response.headers_mut().set(AccessControlAllowOrigin::Any);
+            response.send(ACK).unwrap();
+        }
+    };
+    let (mut server, url) = make_server(handler);
+
+    let origin = Origin::Origin(UrlOrigin::UID(OpaqueOrigin::new()));
+    let mut request = Request::new(url, Some(origin), false);
+    *request.method.borrow_mut() = Method::Extension("CHICKEN".to_owned());
+    request.referer = Referer::NoReferer;
+    request.use_cors_preflight = true;
+    request.mode = RequestMode::CORSMode;
+    let wrapped_request = Rc::new(request);
+
+    let fetch_response = fetch(wrapped_request);
+    let _ = server.close();
+
+    assert!(fetch_response.is_network_error());
+}
+
 #[test]
 fn test_fetch_response_is_basic_filtered() {
 
@@ -342,7 +412,7 @@ fn test_fetch_with_local_urls_only() {
     assert!(server_response.is_network_error());
 }
 
-fn test_fetch_redirect_count(message: &'static [u8], redirect_cap: u32) -> Response {
+fn setup_server_and_fetch(message: &'static [u8], redirect_cap: u32) -> Response {
 
     let handler = move |request: HyperRequest, mut response: HyperResponse| {
 
@@ -382,7 +452,7 @@ fn test_fetch_redirect_count_ceiling() {
     // how many redirects to cause
     let redirect_cap = 20;
 
-    let fetch_response = test_fetch_redirect_count(MESSAGE, redirect_cap);
+    let fetch_response = setup_server_and_fetch(MESSAGE, redirect_cap);
 
     assert!(!fetch_response.is_network_error());
     assert_eq!(fetch_response.response_type, ResponseType::Basic);
@@ -402,7 +472,7 @@ fn test_fetch_redirect_count_failure() {
     // how many redirects to cause
     let redirect_cap = 21;
 
-    let fetch_response = test_fetch_redirect_count(MESSAGE, redirect_cap);
+    let fetch_response = setup_server_and_fetch(MESSAGE, redirect_cap);
 
     assert!(fetch_response.is_network_error());