diff --git a/media/libmedia/mediaplayer.cpp b/media/libmedia/mediaplayer.cpp
index 502ab2d..faf2339 100644
--- a/media/libmedia/mediaplayer.cpp
+++ b/media/libmedia/mediaplayer.cpp
@@ -922,6 +922,7 @@
 }
 
 status_t MediaPlayer::setNextMediaPlayer(const sp<MediaPlayer>& next) {
+    Mutex::Autolock _l(mLock);
     if (mPlayer == NULL) {
         return NO_INIT;
     }