--- a/ipc/glue/MessageChannel.h
+++ b/ipc/glue/MessageChannel.h
@@ -430,25 +430,27 @@ class MessageChannel : HasResultCodes
     // Run on the not current thread.
     void NotifyChannelClosed();
     void NotifyMaybeChannelError();
 
   private:
     // Can be run on either thread
     void AssertWorkerThread() const
     {
+        MOZ_ASSERT(mWorkerLoopID != -1, "Channel hasn't been opened yet");
         MOZ_RELEASE_ASSERT(mWorkerLoopID == MessageLoop::current()->id(),
                            "not on worker thread!");
     }
 
     // The "link" thread is either the I/O thread (ProcessLink) or the
     // other actor's work thread (ThreadLink).  In either case, it is
     // NOT our worker thread.
     void AssertLinkThread() const
     {
+        MOZ_ASSERT(mWorkerLoopID != -1, "Channel hasn't been opened yet");
         MOZ_RELEASE_ASSERT(mWorkerLoopID != MessageLoop::current()->id(),
                            "on worker thread but should not be!");
     }
 
   private:
     class MessageTask :
         public CancelableRunnable,
         public LinkedListElement<RefPtr<MessageTask>>,