diff --git a/libavformat/dhav.c b/libavformat/dhav.c
index e5eef290b8..e6279ea31a 100644
--- a/libavformat/dhav.c
+++ b/libavformat/dhav.c
@@ -279,7 +279,7 @@ static int64_t get_duration(AVFormatContext *s)
         }
     }
 
-    if (pos < buffer_pos || pos + 20 > buffer_pos + buffer_size)
+    if (pos < buffer_pos || pos - buffer_pos > buffer_size - 20)
         goto fail;
 
     date = AV_RL32(buffer + (pos - buffer_pos) + 16);