--- a/dom/media/webrtc/MediaEngineWebRTCAudio.cpp
+++ b/dom/media/webrtc/MediaEngineWebRTCAudio.cpp
@@ -471,17 +471,17 @@ MediaEngineWebRTCMicrophoneSource::Updat
       }
 
       if (prefs.mChannels != mLastPrefs.mChannels) {
         // If the channel count changed, tell the MSG to open a new driver with
         // the correct channel count.
         MOZ_ASSERT(!mAllocations.IsEmpty());
         RefPtr<SourceMediaStream> stream;
         for (const Allocation& allocation : mAllocations) {
-          if (allocation.mStream) {
+          if (allocation.mStream && allocation.mStream->GraphImpl()) {
             stream = allocation.mStream;
             break;
           }
         }
         MOZ_ASSERT(stream);
 
         mAudioInput->SetUserChannelCount(prefs.mChannels);
         // Get validated number of channel