--- a/widget/windows/AudioSession.cpp
+++ b/widget/windows/AudioSession.cpp
@@ -291,20 +291,21 @@ AudioSession::Start()
   mState = STARTED;
 
   return NS_OK;
 }
 
 void
 AudioSession::StopInternal()
 {
-  if (mAudioSessionControl) {
+  if (mAudioSessionControl &&
+      (mState == STARTED || mState == STOPPED)) {
     mAudioSessionControl->UnregisterAudioSessionNotification(this);
-    mAudioSessionControl = nullptr;
   }
+  mAudioSessionControl = nullptr;
 }
 
 nsresult
 AudioSession::Stop()
 {
   MOZ_ASSERT(mState == STARTED ||
              mState == UNINITIALIZED || // XXXremove this
              mState == FAILED,