--- a/dom/media/webrtc/MediaEngineWebRTCAudio.cpp
+++ b/dom/media/webrtc/MediaEngineWebRTCAudio.cpp
@@ -681,18 +681,29 @@ MediaEngineWebRTCMicrophoneSource::Stop(
 
 void
 MediaEngineWebRTCMicrophoneSource::NotifyPull(MediaStreamGraph *aGraph,
                                               SourceMediaStream *aSource,
                                               TrackID aID,
                                               StreamTime aDesiredTime,
                                               const PrincipalHandle& aPrincipalHandle)
 {
-  // Ignore - we push audio data
   LOG_FRAMES(("NotifyPull, desired = %" PRId64, (int64_t) aDesiredTime));
+
+  StreamTime delta = aDesiredTime - aSource->GetEndOfAppendedData(aID);
+  if (delta <= 0) {
+    return;
+  }
+
+  // Not enough data has been pushed so we fill it with silence.
+  // This could be due to underruns or because we have been stopped.
+
+  AudioSegment audio;
+  audio.AppendNullData(delta);
+  aSource->AppendToTrack(aID, &audio);
 }
 
 void
 MediaEngineWebRTCMicrophoneSource::NotifyOutputData(MediaStreamGraph* aGraph,
                                                     AudioDataValue* aBuffer,
                                                     size_t aFrames,
                                                     TrackRate aRate,
                                                     uint32_t aChannels)

--- a/dom/media/webrtc/moz.build
+++ b/dom/media/webrtc/moz.build
@@ -36,16 +36,17 @@ if CONFIG['MOZ_WEBRTC']:
     ]
     # MediaEngineWebRTC.cpp needs to be built separately.
     SOURCES += [
         'MediaEngineWebRTC.cpp',
     ]
     LOCAL_INCLUDES += [
         '..',
         '/dom/base',
+        '/dom/media',
         '/media/libyuv/libyuv/include',
         '/media/webrtc/signaling/src/common',
         '/media/webrtc/signaling/src/common/browser_logging',
         '/media/webrtc/trunk'
     ]
 
 XPIDL_SOURCES += [
     'nsITabSource.idl'