diff --git a/src/components/compositing/compositor.rs b/src/components/compositing/compositor.rs
index 2107928a719..1034ec5f07c 100644
--- a/src/components/compositing/compositor.rs
+++ b/src/components/compositing/compositor.rs
@@ -404,13 +404,20 @@ impl IOCompositor {
             new_root.extra_data.borrow_mut().unrendered_color = unrendered_color;
 
             let parent_layer_id = new_root.extra_data.borrow().id;
-            assert!(CompositorData::add_child_if_necessary(new_root.clone(),
-                                                           root_pipeline_id,
-                                                           parent_layer_id,
+            match CompositorData::find_layer_with_layer_and_pipeline_id(new_root.clone(),
+                                                                        root_pipeline_id,
+                                                                        parent_layer_id) {
+                Some(ref mut parent_layer) => {
+                    CompositorData::add_child_if_necessary(parent_layer.clone(),
                                                            layer_id,
                                                            Rect(Point2D(0f32, 0f32), size),
                                                            size,
-                                                           Scrollable));
+                                                           Scrollable);
+                }
+                None => {
+                    fail!("Compositor: couldn't find parent layer");
+                }
+            }
 
             // Release all tiles from the layer before dropping it.
             match self.scene.root {
@@ -429,19 +436,26 @@ impl IOCompositor {
                                                        rect: Rect<f32>,
                                                        scroll_policy: ScrollPolicy) {
         match self.scene.root {
-            Some(ref root) => {
-                let parent_layer_id = root.extra_data.borrow().id;
-                let page_size = root.extra_data.borrow().page_size.unwrap();
-                assert!(CompositorData::add_child_if_necessary(root.clone(),
-                                                               pipeline_id,
-                                                               parent_layer_id,
+            Some(ref root_layer) => {
+                let parent_layer_id = root_layer.extra_data.borrow().id;
+                match CompositorData::find_layer_with_pipeline_and_layer_id(root_layer.clone(),
+                                                                            pipeline_id,
+                                                                            parent_layer_id) {
+                    Some(ref mut parent_layer) => {
+                        let page_size = root_layer.extra_data.borrow().page_size.unwrap();
+                        CompositorData::add_child_if_necessary(parent_layer.clone(),
                                                                layer_id,
                                                                rect,
                                                                page_size,
-                                                               scroll_policy))
+                                                               scroll_policy);
+                    }
+                    None => {
+                        fail!("Compositor: couldn't find parent layer");
+                    }
+                }
             }
-            None => fail!("Compositor: Received new layer without initialized pipeline"),
-        };
+            None => fail!("Compositor: Received new layer without initialized pipeline")
+        }
 
         self.ask_for_tiles();
     }
diff --git a/src/components/compositing/compositor_data.rs b/src/components/compositing/compositor_data.rs
index 0a72fd955cb..ed67fe1584c 100644
--- a/src/components/compositing/compositor_data.rs
+++ b/src/components/compositing/compositor_data.rs
@@ -146,38 +146,18 @@ impl CompositorData {
     /// Adds a child layer to the layer with the given ID and the given pipeline, if it doesn't
     /// exist yet. The child layer will have the same pipeline, tile size, memory limit, and CPU
     /// painting status as its parent.
-    ///
-    /// Returns:
-    ///   * True if the layer was added;
-    ///   * True if the layer was not added because it already existed;
-    ///   * False if the layer could not be added because no suitable parent layer with the given
-    ///     ID and pipeline could be found.
     pub fn add_child_if_necessary(layer: Rc<Layer<CompositorData>>,
-                                  pipeline_id: PipelineId,
-                                  parent_layer_id: LayerId,
                                   child_layer_id: LayerId,
                                   rect: Rect<f32>,
                                   page_size: Size2D<f32>,
-                                  scroll_policy: ScrollPolicy) -> bool {
-        if layer.extra_data.borrow().pipeline.id != pipeline_id ||
-           layer.extra_data.borrow().id != parent_layer_id {
-            return layer.children().iter().any(|kid| {
-                CompositorData::add_child_if_necessary(kid.clone(),
-                                                       pipeline_id,
-                                                       parent_layer_id,
-                                                       child_layer_id,
-                                                       rect,
-                                                       page_size,
-                                                       scroll_policy)
-            })
-        }
-
+                                  scroll_policy: ScrollPolicy) {
         // See if we've already made this child layer.
+        let pipeline_id = layer.extra_data.borrow().pipeline.id;
         if layer.children().iter().any(|kid| {
                     kid.extra_data.borrow().pipeline.id == pipeline_id &&
                     kid.extra_data.borrow().id == child_layer_id
                 }) {
-            return true
+            return;
         }
 
         let new_compositor_data = CompositorData::new(layer.extra_data.borrow().pipeline.clone(),
@@ -197,8 +177,6 @@ impl CompositorData {
 
         // Place the kid's layer in the container passed in.
         Layer::add_child(layer.clone(), new_kid.clone());
-
-        true
     }
 
     /// Move the layer's descendants that don't want scroll events and scroll by a relative