--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -2019,18 +2019,16 @@ MediaDecoderStateMachine::OnMetadataRead
   if (waitingForCDM) {
     // Metadata parsing was successful but we're still waiting for CDM caps
     // to become available so that we can build the correct decryptor/decoder.
     SetState(DECODER_STATE_WAIT_FOR_CDM);
     return;
   }
 
   SetState(DECODER_STATE_DECODING);
-
-  ScheduleStateMachine();
 }
 
 void
 MediaDecoderStateMachine::OnMetadataNotRead(ReadMetadataFailureReason aReason)
 {
   MOZ_ASSERT(OnTaskQueue());
   MOZ_ASSERT(mState == DECODER_STATE_DECODING_METADATA);
   mMetadataRequest.Complete();
@@ -2193,17 +2191,17 @@ MediaDecoderStateMachine::SeekCompleted(
   mQuickBuffering = false;
 
   if (video) {
     mMediaSink->Redraw(mInfo.mVideo);
     mOnPlaybackEvent.Notify(MediaEventType::Invalidate);
   }
 
   SetState(nextState);
-  ScheduleStateMachine();
+  MOZ_ASSERT(IsStateMachineScheduled());
 }
 
 RefPtr<ShutdownPromise>
 MediaDecoderStateMachine::BeginShutdown()
 {
   return InvokeAsync(OwnerThread(), this, __func__,
                      &MediaDecoderStateMachine::Shutdown);
 }