diff --git a/services/audioflinger/MmapTracks.h b/services/audioflinger/MmapTracks.h
index 0210bc2..259136b 100644
--- a/services/audioflinger/MmapTracks.h
+++ b/services/audioflinger/MmapTracks.h
@@ -78,6 +78,7 @@
     float getPortVolume() const override { return mVolume; }
     bool getPortMute() const override { return mMutedFromPort; }
 
+    std::string trackFlagsAsString() const final { return {}; }
 private:
     DISALLOW_COPY_AND_ASSIGN(MmapTrack);