diff --git a/libavformat/mpeg.c b/libavformat/mpeg.c
index a362e29e8b..93b5f40d5f 100644
--- a/libavformat/mpeg.c
+++ b/libavformat/mpeg.c
@@ -78,7 +78,7 @@ static int mpegps_probe(AVProbeData *p)
     for(i=0; i<p->buf_size; i++){
         code = (code<<8) + p->buf[i];
         if ((code & 0xffffff00) == 0x100) {
-            int pes= check_pes(p->buf+i, p->buf+i+p->buf_size);
+            int pes= check_pes(p->buf+i, p->buf+p->buf_size);
 
             if(code == SYSTEM_HEADER_START_CODE) sys++;
             else if(code == PRIVATE_STREAM_1)    priv1++;