diff --git a/framework/server/com/libremobileos/faceunlock/server/CameraService.java b/framework/server/com/libremobileos/faceunlock/server/CameraService.java
index 9237544..1690907 100644
--- a/framework/server/com/libremobileos/faceunlock/server/CameraService.java
+++ b/framework/server/com/libremobileos/faceunlock/server/CameraService.java
@@ -113,13 +113,13 @@
 		}
 	};
 
-	public void startBackgroundThread() {
+	public synchronized void startBackgroundThread() {
 		mBackgroundThread = new HandlerThread("Camera Background");
 		mBackgroundThread.start();
 		mBackgroundHandler = new Handler(mBackgroundThread.getLooper());
 	}
 
-	public void stopBackgroundThread() {
+	public synchronized void stopBackgroundThread() {
 		closeCamera();
 		mBackgroundThread.quitSafely();
 		try {
@@ -382,4 +382,4 @@
 		}
 		Trace.endSection();
 	}
-}
\ No newline at end of file
+}