diff --git a/libavcodec/mjpegdec.c b/libavcodec/mjpegdec.c
index be85fc55a0..1608b4f9e2 100644
--- a/libavcodec/mjpegdec.c
+++ b/libavcodec/mjpegdec.c
@@ -1140,7 +1140,7 @@ static int mjpeg_decode_scan_progressive_ac(MJpegDecodeContext *s, int ss,
     }
 
     if (!Al) {
-        s->coefs_finished[c] |= (1LL << (se + 1)) - (1LL << ss);
+        s->coefs_finished[c] |= (2LL << se) - (1LL << ss);
         last_scan = !~s->coefs_finished[c];
     }