diff --git a/libavcodec/pnm_parser.c b/libavcodec/pnm_parser.c
index 5339bebde9..58c3cd2431 100644
--- a/libavcodec/pnm_parser.c
+++ b/libavcodec/pnm_parser.c
@@ -92,8 +92,11 @@ retry:
             sync = bs;
             c = *bs++;
             if (c == '#')  {
-                while (c != '\n' && bs < end)
-                    c = *bs++;
+                uint8_t *match = memchr(bs, '\n', end-bs);
+                if (match)
+                    bs = match + 1;
+                else
+                    break;
             } else if (c == 'P') {
                 next = bs - pnmctx.bytestream_start + skip - 1;
                 pnmpc->ascii_scan = 0;