diff --git a/libavformat/dhav.c b/libavformat/dhav.c
index 449e5bfb0a..598780e8b8 100644
--- a/libavformat/dhav.c
+++ b/libavformat/dhav.c
@@ -252,7 +252,7 @@ static int64_t get_duration(AVFormatContext *s)
     int64_t size = avio_size(s->pb);
     int64_t ret = 0;
 
-    if (start_pos + 20 > size)
+    if (start_pos < 0 || start_pos > size - 20)
         return 0;
 
     avio_skip(s->pb, 16);