--- a/dom/media/webaudio/MediaStreamAudioSourceNode.cpp
+++ b/dom/media/webaudio/MediaStreamAudioSourceNode.cpp
@@ -91,16 +91,18 @@ MediaStreamAudioSourceNode::~MediaStream
 {
   Destroy();
 }
 
 void
 MediaStreamAudioSourceNode::AttachToTrack(const RefPtr<MediaStreamTrack>& aTrack)
 {
   MOZ_ASSERT(!mInputTrack);
+  MOZ_ASSERT(aTrack->AsAudioStreamTrack());
+
   if (!mStream) {
     return;
   }
 
   mInputTrack = aTrack;
   ProcessedMediaStream* outputStream =
     static_cast<ProcessedMediaStream*>(mStream.get());
   mInputPort = mInputTrack->ForwardTrackContentsTo(outputStream);
@@ -143,16 +145,20 @@ MediaStreamAudioSourceNode::AttachToFirs
 
 void
 MediaStreamAudioSourceNode::NotifyTrackAdded(const RefPtr<MediaStreamTrack>& aTrack)
 {
   if (mInputTrack) {
     return;
   }
 
+  if (!aTrack->AsAudioStreamTrack()) {
+    return;
+  }
+
   AttachToTrack(aTrack);
 }
 
 void
 MediaStreamAudioSourceNode::NotifyTrackRemoved(const RefPtr<MediaStreamTrack>& aTrack)
 {
   if (aTrack != mInputTrack) {
     return;