diff --git a/components/style/gecko/wrapper.rs b/components/style/gecko/wrapper.rs
index aadf55dd6a7..e8bfdf6dbc7 100644
--- a/components/style/gecko/wrapper.rs
+++ b/components/style/gecko/wrapper.rs
@@ -1409,19 +1409,36 @@ impl<'le> TElement for GeckoElement<'le> {
         // If we are a NAC pseudo-element, we want to get rules from our
         // rule_hash_target, that is, our originating element.
         let mut current = Some(self.rule_hash_target());
-
         while let Some(element) = current {
+            // TODO(emilio): Deal with Shadow DOM separately than with XBL
+            // (right now we still rely on get_xbl_binding_parent()).
+            //
+            // That will allow to clean up a bunch in
+            // push_applicable_declarations.
+            if let Some(shadow) = element.shadow_root() {
+                debug_assert!(!shadow.mServoStyles.mPtr.is_null());
+                let author_styles = unsafe {
+                    &*(shadow.mServoStyles.mPtr
+                        as *const structs::RawServoAuthorStyles
+                        as *const bindings::RawServoAuthorStyles)
+                };
+
+                let author_styles: &'a _ = AuthorStyles::<GeckoStyleSheet>::from_ffi(author_styles);
+                f(&author_styles.data, author_styles.quirks_mode);
+                if element != *self {
+                    break;
+                }
+            }
+
             if let Some(binding) = element.xbl_binding() {
                 binding.each_xbl_cascade_data(&mut f);
 
                 // If we're not looking at our original element, allow the
                 // binding to cut off style inheritance.
-                if element != *self {
-                    if !binding.inherits_style() {
-                        // Go no further; we're not inheriting style from
-                        // anything above here.
-                        break;
-                    }
+                if element != *self && !binding.inherits_style() {
+                    // Go no further; we're not inheriting style from
+                    // anything above here.
+                    break;
                 }
             }
 
diff --git a/ports/geckolib/glue.rs b/ports/geckolib/glue.rs
index 9f6a64e0dd1..1896b87fa71 100644
--- a/ports/geckolib/glue.rs
+++ b/ports/geckolib/glue.rs
@@ -1149,6 +1149,40 @@ pub unsafe extern "C" fn Servo_AuthorStyles_AppendStyleSheet(
     styles.stylesheets.append_stylesheet(None, sheet, &guard);
 }
 
+#[no_mangle]
+pub unsafe extern "C" fn Servo_AuthorStyles_InsertStyleSheetBefore(
+    styles: RawServoAuthorStylesBorrowedMut,
+    sheet: *const ServoStyleSheet,
+    before_sheet: *const ServoStyleSheet,
+) {
+    let styles = AuthorStyles::<GeckoStyleSheet>::from_ffi_mut(styles);
+
+    let global_style_data = &*GLOBAL_STYLE_DATA;
+    let guard = global_style_data.shared_lock.read();
+    styles.stylesheets.insert_stylesheet_before(
+        None,
+        GeckoStyleSheet::new(sheet),
+        GeckoStyleSheet::new(before_sheet),
+        &guard,
+    );
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn Servo_AuthorStyles_RemoveStyleSheet(
+    styles: RawServoAuthorStylesBorrowedMut,
+    sheet: *const ServoStyleSheet,
+) {
+    let styles = AuthorStyles::<GeckoStyleSheet>::from_ffi_mut(styles);
+
+    let global_style_data = &*GLOBAL_STYLE_DATA;
+    let guard = global_style_data.shared_lock.read();
+    styles.stylesheets.remove_stylesheet(
+        None,
+        GeckoStyleSheet::new(sheet),
+        &guard,
+    );
+}
+
 #[no_mangle]
 pub unsafe extern "C" fn Servo_AuthorStyles_ForceDirty(
     styles: RawServoAuthorStylesBorrowedMut,