diff --git a/src/components/main/compositing/run.rs b/src/components/main/compositing/run.rs
index 3f48199c268..cd9b44d74bb 100644
--- a/src/components/main/compositing/run.rs
+++ b/src/components/main/compositing/run.rs
@@ -426,4 +426,8 @@ pub fn run_compositor(compositor: &CompositorTask) {
         None => {}
         Some(ref mut layer) => layer.forget_all_tiles(),
     }
+
+    // Drain compositor port, sometimes messages contain channels that are blocking
+    // another task from finishing (i.e. SetIds)
+    while compositor.port.peek() { compositor.port.recv(); }
 }
diff --git a/src/components/main/constellation.rs b/src/components/main/constellation.rs
index bdd1b87c8d5..aa63afb6fc2 100644
--- a/src/components/main/constellation.rs
+++ b/src/components/main/constellation.rs
@@ -807,9 +807,13 @@ impl Constellation {
     fn set_ids(&self, frame_tree: @mut FrameTree) {
         let (port, chan) = comm::stream();
         self.compositor_chan.send(SetIds(frame_tree.to_sendable(), chan, self.chan.clone()));
-        port.try_recv();
-        for frame in frame_tree.iter() {
-            frame.pipeline.grant_paint_permission();
+        match port.try_recv() {
+            Some(()) => {
+                for frame in frame_tree.iter() {
+                    frame.pipeline.grant_paint_permission();
+                }
+            }
+            None => {} // message has been discarded, probably shutting down
         }
     }
 }