diff --git a/components/layout/layout_task.rs b/components/layout/layout_task.rs
index deda7d481c7..d187aa1a37f 100644
--- a/components/layout/layout_task.rs
+++ b/components/layout/layout_task.rs
@@ -40,7 +40,7 @@ use script::layout_interface::{ContentBoxesQuery, ContentBoxQuery, ExitNowMsg, G
 use script::layout_interface::{HitTestResponse, LayoutChan, LayoutRPC, LoadStylesheetMsg};
 use script::layout_interface::{MouseOverResponse, Msg, NoQuery, PrepareToExitMsg};
 use script::layout_interface::{ReapLayoutDataMsg, Reflow, ReflowForDisplay, ReflowMsg};
-use script::layout_interface::{ScriptLayoutChan, TrustedNodeAddress};
+use script::layout_interface::{ScriptLayoutChan, SetQuirksModeMsg, TrustedNodeAddress};
 use script_traits::{SendEventMsg, ReflowEvent, ReflowCompleteMsg, OpaqueScriptLayoutChannel};
 use script_traits::{ScriptControlChan, UntrustedNodeAddress};
 use servo_msg::compositor_msg::Scrollable;
@@ -390,6 +390,7 @@ impl LayoutTask {
         match request {
             AddStylesheetMsg(sheet) => self.handle_add_stylesheet(sheet, possibly_locked_rw_data),
             LoadStylesheetMsg(url) => self.handle_load_stylesheet(url, possibly_locked_rw_data),
+            SetQuirksModeMsg => self.handle_set_quirks_mode(possibly_locked_rw_data),
             GetRPCMsg(response_chan) => {
                 response_chan.send(box LayoutRPCImpl(self.rw_data.clone()) as
                                    Box<LayoutRPC + Send>);
@@ -500,6 +501,15 @@ impl LayoutTask {
         LayoutTask::return_rw_data(possibly_locked_rw_data, rw_data);
     }
 
+    /// Sets quirks mode for the document, causing the quirks mode stylesheet to be loaded.
+    fn handle_set_quirks_mode<'a>(&'a self,
+                                  possibly_locked_rw_data:
+                                    &mut Option<MutexGuard<'a, LayoutTaskData>>) {
+        let mut rw_data = self.lock_rw_data(possibly_locked_rw_data);
+        rw_data.stylist.add_quirks_mode_stylesheet();
+        LayoutTask::return_rw_data(possibly_locked_rw_data, rw_data);
+    }
+
     /// Retrieves the flow tree root from the root node.
     fn try_get_layout_root(&self, node: LayoutNode) -> Option<FlowRef> {
         let mut layout_data_ref = node.mutate_layout_data();
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index c4dc787ac26..4fdb8a9befd 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -61,6 +61,7 @@ use servo_util::namespace;
 use servo_util::str::{DOMString, split_html_space_chars};
 
 use html5ever::tree_builder::{QuirksMode, NoQuirks, LimitedQuirks, Quirks};
+use layout_interface::{LayoutChan, SetQuirksModeMsg};
 use string_cache::{Atom, QualName};
 use url::Url;
 
@@ -217,6 +218,15 @@ impl<'a> DocumentHelpers<'a> for JSRef<'a, Document> {
 
     fn set_quirks_mode(self, mode: QuirksMode) {
         self.quirks_mode.set(mode);
+
+        match mode {
+            Quirks => {
+                let window = self.window.root();
+                let LayoutChan(ref layout_chan) = window.page().layout_chan;
+                layout_chan.send(SetQuirksModeMsg);
+            }
+            NoQuirks | LimitedQuirks => {}
+        }
     }
 
     fn set_last_modified(self, value: DOMString) {
diff --git a/components/script/layout_interface.rs b/components/script/layout_interface.rs
index c3afb15c057..0f3f4fbacbf 100644
--- a/components/script/layout_interface.rs
+++ b/components/script/layout_interface.rs
@@ -29,6 +29,9 @@ pub enum Msg {
     /// Adds the given stylesheet to the document.
     LoadStylesheetMsg(Url),
 
+    /// Puts a document into quirks mode, causing the quirks mode stylesheet to be loaded.
+    SetQuirksModeMsg,
+
     /// Requests a reflow.
     ReflowMsg(Box<Reflow>),
 
diff --git a/components/style/selector_matching.rs b/components/style/selector_matching.rs
index 6d868028894..1e1acaf918a 100644
--- a/components/style/selector_matching.rs
+++ b/components/style/selector_matching.rs
@@ -292,7 +292,6 @@ impl Stylist {
             after_map: PerPseudoElementSelectorMap::new(),
             rules_source_order: 0u,
         };
-        // FIXME: Add quirks-mode.css in quirks mode.
         // FIXME: Add iso-8859-9.css when the document’s encoding is ISO-8859-8.
         // FIXME: presentational-hints.css should be at author origin with zero specificity.
         //        (Does it make a difference?)
@@ -388,6 +387,15 @@ impl Stylist {
         self.is_dirty |= is_dirty;
     }
 
+    pub fn add_quirks_mode_stylesheet(&mut self) {
+        self.add_stylesheet(Stylesheet::from_bytes(
+            read_resource_file(["quirks-mode.css"]).unwrap().as_slice(),
+            Url::parse("chrome:///quirks-mode.css").unwrap(),
+            None,
+            None,
+            UserAgentOrigin))
+    }
+
     pub fn add_stylesheet(&mut self, stylesheet: Stylesheet) {
         self.stylesheets.push(stylesheet);
         self.is_dirty = true;