diff --git a/libavformat/swfdec.c b/libavformat/swfdec.c
index 9a0b27bd8c..e427998744 100644
--- a/libavformat/swfdec.c
+++ b/libavformat/swfdec.c
@@ -78,10 +78,9 @@ static int swf_probe(const AVProbeData *p)
         && p->buf[3] <= 20)
         return AVPROBE_SCORE_MAX / 4 + 1;
 
-    if (init_get_bits8(&gb, p->buf + 3, p->buf_size - 3) < 0)
+    if (init_get_bits8(&gb, p->buf + 8, p->buf_size - 8) < 0)
         return 0;
 
-    skip_bits(&gb, 40);
     len = get_bits(&gb, 5);
     if (!len)
         return 0;