diff --git a/libavformat/wtv.c b/libavformat/wtv.c
index b0039051f9..50997398a5 100644
--- a/libavformat/wtv.c
+++ b/libavformat/wtv.c
@@ -269,7 +269,12 @@ static AVIOContext * wtvfile_open2(AVFormatContext *s, const uint8_t *buf, int b
         dir_length  = AV_RL16(buf + 16);
         file_length = AV_RL64(buf + 24);
         name_size   = 2 * AV_RL32(buf + 32);
-        if (buf + 48 + name_size > buf_end) {
+        if (name_size < 0) {
+            av_log(s, AV_LOG_ERROR,
+                   "bad filename length, remaining directory entries ignored\n");
+            break;
+        }
+        if (48 + name_size > buf_end - buf) {
             av_log(s, AV_LOG_ERROR, "filename exceeds buffer size; remaining directory entries ignored\n");
             break;
         }