diff --git a/services/audiopolicy/AudioPolicyService.h b/services/audiopolicy/AudioPolicyService.h
index 4e68ab1..f1db309 100644
--- a/services/audiopolicy/AudioPolicyService.h
+++ b/services/audiopolicy/AudioPolicyService.h
@@ -495,7 +495,7 @@
     AudioPolicyClient *mAudioPolicyClient;
 
     DefaultKeyedVector< uid_t, sp<NotificationClient> >    mNotificationClients;
-
+    Mutex mNotificationClientsLock;  // protects mNotificationClients
     // Manage all effects configured in audio_effects.conf
     sp<AudioPolicyEffects> mAudioPolicyEffects;
     audio_mode_t mPhoneState;