diff --git a/media/libheif/HeifDecoderImpl.h b/media/libheif/HeifDecoderImpl.h
index 86a8628..c1504cd 100644
--- a/media/libheif/HeifDecoderImpl.h
+++ b/media/libheif/HeifDecoderImpl.h
@@ -72,6 +72,8 @@
     bool mHasVideo;
     size_t mSequenceLength;
 
+    Mutex mRetrieverLock;
+
     // Slice decoding only
     Mutex mLock;
     Condition mScanlineReady;