diff --git a/components/layout_thread/lib.rs b/components/layout_thread/lib.rs
index edba3c6ad45b..4428c0c47710 100644
--- a/components/layout_thread/lib.rs
+++ b/components/layout_thread/lib.rs
@@ -1085,6 +1085,7 @@ impl LayoutThread {
             ua_or_user: &ua_or_user_guard,
         };
         let mut extra_data = ExtraStyleData {
+            author_style_disabled: None,
             marker: PhantomData,
         };
         let needs_dirtying = Arc::get_mut(&mut rw_data.stylist).unwrap().update(
diff --git a/components/style/gecko/data.rs b/components/style/gecko/data.rs
index b3b6402f0c99..4ad43d3594af 100644
--- a/components/style/gecko/data.rs
+++ b/components/style/gecko/data.rs
@@ -32,6 +32,9 @@ pub struct PerDocumentStyleDataImpl {
     /// Whether the stylesheets list above has changed since the last restyle.
     pub stylesheets_changed: bool,
 
+    /// Has author style been disabled?
+    pub author_style_disabled: bool,
+
     // FIXME(bholley): Hook these up to something.
     /// Unused. Will go away when we actually implement transitions and
     /// animations properly.
@@ -65,6 +68,7 @@ impl PerDocumentStyleData {
             stylist: Arc::new(Stylist::new(device)),
             stylesheets: vec![],
             stylesheets_changed: true,
+            author_style_disabled: false,
             new_animations_sender: new_anims_sender,
             new_animations_receiver: new_anims_receiver,
             running_animations: Arc::new(RwLock::new(HashMap::new())),
@@ -103,6 +107,7 @@ impl PerDocumentStyleDataImpl {
             let mut stylist = Arc::get_mut(&mut self.stylist).unwrap();
             let mut extra_data = ExtraStyleData {
                 font_faces: &mut self.font_faces,
+                author_style_disabled: Some(self.author_style_disabled),
             };
             stylist.update(&self.stylesheets, &StylesheetGuards::same(guard),
                            None, true, &mut extra_data);
diff --git a/components/style/gecko_bindings/bindings.rs b/components/style/gecko_bindings/bindings.rs
index 87ca62981a42..29f0e5001710 100644
--- a/components/style/gecko_bindings/bindings.rs
+++ b/components/style/gecko_bindings/bindings.rs
@@ -1525,7 +1525,8 @@ extern "C" {
 }
 extern "C" {
     pub fn Servo_StyleSet_NoteStyleSheetsChanged(set:
-                                                     RawServoStyleSetBorrowed);
+                                                     RawServoStyleSetBorrowed,
+                                                 author_style_disabled: bool);
 }
 extern "C" {
     pub fn Servo_StyleSet_FillKeyframesForName(set: RawServoStyleSetBorrowed,
diff --git a/components/style/stylist.rs b/components/style/stylist.rs
index 0d43f320d246..5987dd74e447 100644
--- a/components/style/stylist.rs
+++ b/components/style/stylist.rs
@@ -78,6 +78,9 @@ pub struct Stylist {
     /// If true, the quirks-mode stylesheet is applied.
     quirks_mode: bool,
 
+    /// If true, authored styles are ignored.
+    author_style_disabled: bool,
+
     /// If true, the device has changed, and the stylist needs to be updated.
     is_device_dirty: bool,
 
@@ -134,6 +137,10 @@ pub struct ExtraStyleData<'a> {
     #[cfg(feature = "gecko")]
     pub font_faces: &'a mut Vec<(Arc<Locked<FontFaceRule>>, Origin)>,
 
+    /// A parameter to change a setting to ignore author styles during update.
+    /// A None value indicates that update should use existing settings.
+    pub author_style_disabled: Option<bool>,
+
     #[allow(missing_docs)]
     #[cfg(feature = "servo")]
     pub marker: PhantomData<&'a usize>,
@@ -167,6 +174,7 @@ impl Stylist {
             device: Arc::new(device),
             is_device_dirty: true,
             quirks_mode: false,
+            author_style_disabled: false,
 
             element_map: PerPseudoElementSelectorMap::new(),
             pseudos_map: Default::default(),
@@ -274,7 +282,16 @@ impl Stylist {
             }
         }
 
-        for ref stylesheet in doc_stylesheets.iter() {
+        // Absorb changes to author_style_disabled, if supplied.
+        if let Some(author_style_disabled) = extra_data.author_style_disabled {
+            self.author_style_disabled = author_style_disabled;
+        }
+
+        // Only use author stylesheets if author styles are enabled.
+        let author_style_enabled = !self.author_style_disabled;
+        let sheets_to_add = doc_stylesheets.iter().filter(
+            |&s| author_style_enabled || s.origin != Origin::Author);
+        for ref stylesheet in sheets_to_add {
             self.add_stylesheet(stylesheet, guards.author, extra_data);
         }
 
diff --git a/ports/geckolib/glue.rs b/ports/geckolib/glue.rs
index b321efe467a8..96939ec39943 100644
--- a/ports/geckolib/glue.rs
+++ b/ports/geckolib/glue.rs
@@ -645,9 +645,11 @@ pub extern "C" fn Servo_StyleSet_FlushStyleSheets(raw_data: RawServoStyleSetBorr
 }
 
 #[no_mangle]
-pub extern "C" fn Servo_StyleSet_NoteStyleSheetsChanged(raw_data: RawServoStyleSetBorrowed) {
+pub extern "C" fn Servo_StyleSet_NoteStyleSheetsChanged(raw_data: RawServoStyleSetBorrowed,
+                                                        author_style_disabled: bool) {
     let mut data = PerDocumentStyleData::from_ffi(raw_data).borrow_mut();
     data.stylesheets_changed = true;
+    data.author_style_disabled = author_style_disabled;
 }
 
 #[no_mangle]