--- a/dom/media/MediaShutdownManager.cpp
+++ b/dom/media/MediaShutdownManager.cpp
@@ -44,17 +44,17 @@ MediaShutdownManager::Instance()
     sInstance = new MediaShutdownManager();
   }
   return *sInstance;
 }
 
 void
 MediaShutdownManager::EnsureCorrectShutdownObserverState()
 {
-  MOZ_ASSERT(!mIsDoingXPCOMShutDown);
+  MOZ_DIAGNOSTIC_ASSERT(!mIsDoingXPCOMShutDown);
   bool needShutdownObserver = mDecoders.Count() > 0;
   if (needShutdownObserver != mIsObservingShutdown) {
     mIsObservingShutdown = needShutdownObserver;
     if (mIsObservingShutdown) {
       nsContentUtils::RegisterShutdownObserver(this);
     } else {
       nsContentUtils::UnregisterShutdownObserver(this);
       // Clear our singleton reference. This will probably delete