--- a/dom/html/HTMLMediaElement.cpp
+++ b/dom/html/HTMLMediaElement.cpp
@@ -3866,17 +3866,21 @@ public:
     WatchTarget(aName),
     mElement(aElement),
     mHaveCurrentData(false),
     mBlocked(false),
     mFinished(false),
     mMutex(aName),
     mPendingNotifyOutput(false)
   {}
-  void Forget() { mElement = nullptr; }
+  void Forget()
+  {
+    mElement = nullptr;
+    NotifyWatchers();
+  }
 
   // Main thread
 
   MediaDecoderOwner::NextFrameStatus NextFrameStatus()
   {
     if (!mElement || !mHaveCurrentData || mFinished) {
       return MediaDecoderOwner::NEXT_FRAME_UNAVAILABLE;
     }