diff --git a/libavcodec/pnm_parser.c b/libavcodec/pnm_parser.c
index 036ee97914..bdb2d07823 100644
--- a/libavcodec/pnm_parser.c
+++ b/libavcodec/pnm_parser.c
@@ -62,7 +62,7 @@ retry:
     } else {
         int ret = av_image_get_buffer_size(avctx->pix_fmt, avctx->width, avctx->height, 1);
         next = pnmctx.bytestream - pnmctx.bytestream_start;
-        if (ret >= 0)
+        if (ret >= 0 && next + (uint64_t)ret <= INT_MAX)
             next += ret;
         if (pnmctx.bytestream_start != buf)
             next -= pc->index;