diff --git a/library/src/jp/co/cyberagent/android/gpuimage/GPUImageMovieWriter.java b/library/src/jp/co/cyberagent/android/gpuimage/GPUImageMovieWriter.java
index 090ad7e69..c52ee1970 100644
--- a/library/src/jp/co/cyberagent/android/gpuimage/GPUImageMovieWriter.java
+++ b/library/src/jp/co/cyberagent/android/gpuimage/GPUImageMovieWriter.java
@@ -43,7 +43,7 @@ public void onInit() {
     }
 
     @Override
-    public void onDraw(int textureId, FloatBuffer cubeBuffer, FloatBuffer textureBuffer) {
+    public synchronized void onDraw(int textureId, FloatBuffer cubeBuffer, FloatBuffer textureBuffer) {
         // Draw on screen surface
         super.onDraw(textureId, cubeBuffer, textureBuffer);
 
@@ -71,7 +71,7 @@ public void onDestroy() {
         releaseEncodeSurface();
     }
 
-    public void startRecording(final String outputPath, final int width, final int height) {
+    public synchronized void startRecording(final String outputPath, final int width, final int height) {
         runOnDraw(new Runnable() {
             @Override
             public void run() {
@@ -98,7 +98,7 @@ public void run() {
         });
     }
 
-    public void stopRecording() {
+    public synchronized void stopRecording() {
         runOnDraw(new Runnable() {
             @Override
             public void run() {