--- a/dom/media/MediaStreamGraph.cpp
+++ b/dom/media/MediaStreamGraph.cpp
@@ -1001,22 +1001,23 @@ MediaStreamGraphImpl::CloseAudioInputImp
   MonitorAutoLock mon(mMonitor);
   if (mLifecycleState == LIFECYCLE_RUNNING) {
     GraphDriver* driver;
     if (audioTrackPresent) {
       // We still have audio output
       STREAM_LOG(LogLevel::Debug, ("CloseInput: output present (AudioCallback)"));
 
       driver = new AudioCallbackDriver(this);
-    } else {
+      CurrentDriver()->SwitchAtNextIteration(driver);
+    } else if (CurrentDriver()->AsAudioCallbackDriver()) {
       STREAM_LOG(LogLevel::Debug, ("CloseInput: no output present (SystemClockCallback)"));
 
       driver = new SystemClockDriver(this);
-    }
-    CurrentDriver()->SwitchAtNextIteration(driver);
+      CurrentDriver()->SwitchAtNextIteration(driver);
+    } // else SystemClockDriver->SystemClockDriver, no switch
   }
 }
 
 void
 MediaStreamGraphImpl::CloseAudioInput(AudioDataListener *aListener)
 {
   // So, so, so annoying.  Can't AppendMessage except on Mainthread
   if (!NS_IsMainThread()) {