diff --git a/dom/media/MediaStreamGraphImpl.h b/dom/media/MediaStreamGraphImpl.h
index beb0b8c95dcc..0cbbb165b1ad 100644
--- a/dom/media/MediaStreamGraphImpl.h
+++ b/dom/media/MediaStreamGraphImpl.h
@@ -396,6 +396,9 @@ public:
    */
   bool IsEmpty() const
   {
+    MOZ_ASSERT(OnGraphThreadOrNotRunning() ||
+               (NS_IsMainThread() &&
+                LifecycleStateRef() >= LIFECYCLE_WAITING_FOR_MAIN_THREAD_CLEANUP));
     return mStreams.IsEmpty() && mSuspendedStreams.IsEmpty() && mPortCount == 0;
   }