diff --git a/media/libstagefright/MPEG4Extractor.cpp b/media/libstagefright/MPEG4Extractor.cpp
index 2eb7e5c..be3bc4a 100644
--- a/media/libstagefright/MPEG4Extractor.cpp
+++ b/media/libstagefright/MPEG4Extractor.cpp
@@ -1144,7 +1144,7 @@
         {
             *offset += chunk_size;
 
-            if (chunk_data_size < 4) {
+            if (chunk_data_size < 4 || mLastTrack == NULL) {
                 return ERROR_MALFORMED;
             }