--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -438,16 +438,17 @@ public:
     if (mMaster->CheckIfDecodeComplete()) {
       SetState(DECODER_STATE_COMPLETED);
       return;
     }
 
     mDecodeStartTime = TimeStamp::Now();
 
     mMaster->mIsPrerolling = true;
+    mMaster->MaybeStopPrerolling();
 
     // Ensure that we've got tasks enqueued to decode data if we need to.
     mMaster->DispatchDecodeTasksIfNeeded();
 
     mMaster->ScheduleStateMachine();
   }
 
   void Exit() override