diff --git a/libavformat/asfenc.c b/libavformat/asfenc.c
index 6cc19c7274..85748c76b7 100644
--- a/libavformat/asfenc.c
+++ b/libavformat/asfenc.c
@@ -884,7 +884,7 @@ static int asf_write_trailer(AVFormatContext *s)
         asf_write_header1(s, file_size, data_size - asf->data_offset);
     }
 
-    av_free(asf->index_ptr);
+    av_freep(&asf->index_ptr);
     return 0;
 }