--- a/dom/media/GraphDriver.cpp
+++ b/dom/media/GraphDriver.cpp
@@ -607,16 +607,18 @@ AudioCallbackDriver::Init()
     mAudioStream.own(stream);
   } else {
     NS_WARNING("Could not create a cubeb stream for MediaStreamGraph, falling back to a SystemClockDriver");
     // Fall back to a driver using a normal thread.
     mNextDriver = new SystemClockDriver(GraphImpl());
     mNextDriver->SetGraphTime(this, mIterationStart, mIterationEnd,
                                mStateComputedTime, mNextStateComputedTime);
     mGraphImpl->SetCurrentDriver(mNextDriver);
+    bool found = mGraphImpl->RemoveMixerCallback(this);
+    NS_WARN_IF_FALSE(!found, "Mixer callback not added when switching?");
     mNextDriver->Start();
     return;
   }
 
   cubeb_stream_register_device_changed_callback(mAudioStream,
                                                 AudioCallbackDriver::DeviceChangedCallback_s);
 
   StartStream();

--- a/dom/media/MediaStreamGraphImpl.h
+++ b/dom/media/MediaStreamGraphImpl.h
@@ -425,16 +425,21 @@ public:
   /**
    * Not safe to call off the MediaStreamGraph thread unless monitor is held!
    */
   GraphDriver* CurrentDriver() {
     AssertOnGraphThreadOrNotRunning();
     return mDriver;
   }
 
+  bool RemoveMixerCallback(MixerCallbackReceiver* aReceiver)
+  {
+    return mMixer.RemoveCallback(aReceiver);
+  }
+
   /**
    * Effectively set the new driver, while we are switching.
    * It is only safe to call this at the very end of an iteration, when there
    * has been a SwitchAtNextIteration call during the iteration. The driver
    * should return and pass the control to the new driver shortly after.
    * We can also switch from Revive() (on MainThread), in which case the
    * monitor is held
    */