--- a/dom/media/MediaCache.cpp
+++ b/dom/media/MediaCache.cpp
@@ -2251,20 +2251,20 @@ MediaCacheStream::NotifyDataEnded(uint32
 void
 MediaCacheStream::NotifyClientSuspended(bool aSuspended)
 {
   MOZ_ASSERT(NS_IsMainThread());
 
   RefPtr<ChannelMediaResource> client = mClient;
   nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(
     "MediaCacheStream::NotifyClientSuspended", [client, this, aSuspended]() {
-      if (mClientSuspended != aSuspended) {
+      ReentrantMonitorAutoEnter mon(mMediaCache->GetReentrantMonitor());
+      if (!mClosed && mClientSuspended != aSuspended) {
         mClientSuspended = aSuspended;
         // mClientSuspended changes the decision of reading streams.
-        ReentrantMonitorAutoEnter mon(mMediaCache->GetReentrantMonitor());
         mMediaCache->QueueUpdate();
       }
     });
   OwnerThread()->Dispatch(r.forget());
 }
 
 MediaCacheStream::~MediaCacheStream()
 {