--- a/dom/media/tests/mochitest/pc.js
+++ b/dom/media/tests/mochitest/pc.js
@@ -1096,20 +1096,26 @@ function PeerConnectionWrapper(label, co
 
   /**
    * Callback for native peer connection 'onaddstream' events.
    *
    * @param {Object} event
    *        Event data which includes the stream to be added
    */
   this._pc.onaddstream = function (event) {
-    info(self + ": 'onaddstream' event fired for " + event.stream);
+    info(self + ": 'onaddstream' event fired for " + JSON.stringify(event.stream));
 
-    // TODO: Bug 834835 - Assume type is video until we get get{Audio,Video}Tracks.
-    self.attachMedia(event.stream, 'video', 'remote');
+    var type = '';
+    if (event.stream.getAudioTracks().length > 0) {
+      type = 'audio';
+    }
+    if (event.stream.getVideoTracks().length > 0) {
+      type += 'video';
+    }
+    self.attachMedia(event.stream, type, 'remote');
    };
 
   /**
    * Callback for native peer connection 'ondatachannel' events. If no custom handler
    * has been specified via 'this.ondatachannel', a failure will be raised if an
    * event of this type gets caught.
    *
    * @param {Object} event