diff --git a/libavformat/h263dec.c b/libavformat/h263dec.c
index e6e0345b69..19ed6a94ca 100644
--- a/libavformat/h263dec.c
+++ b/libavformat/h263dec.c
@@ -35,7 +35,7 @@ static int h263_probe(AVProbeData *p)
     for(i=0; i<p->buf_size; i++){
         code = (code<<8) + p->buf[i];
         if ((code & 0xfffffc0000) == 0x800000) {
-            src_fmt= (code>>2)&3;
+            src_fmt= (code>>2)&7;
             if(   src_fmt != last_src_fmt
                && last_src_fmt>0 && last_src_fmt<6
                && src_fmt<6)