diff --git a/libavcodec/h264.c b/libavcodec/h264.c
index 40ba4eb955..9cdac24605 100644
--- a/libavcodec/h264.c
+++ b/libavcodec/h264.c
@@ -7505,7 +7505,7 @@ static int decode_nal_units(H264Context *h, const uint8_t *buf, int buf_size){
             nalsize = 0;
             for(i = 0; i < h->nal_length_size; i++)
                 nalsize = (nalsize << 8) | buf[buf_index++];
-            if(nalsize <= 1 || (nalsize+buf_index > buf_size)){
+            if(nalsize <= 1 || nalsize > buf_size - buf_index){
                 if(nalsize == 1){
                     buf_index++;
                     continue;