diff --git a/libavcodec/dirac_parser.c b/libavcodec/dirac_parser.c
index a7c7c328ad..a2a22ee5b2 100644
--- a/libavcodec/dirac_parser.c
+++ b/libavcodec/dirac_parser.c
@@ -161,7 +161,9 @@ static int dirac_combine_frame(AVCodecParserContext *s, AVCodecContext *avctx,
          * we can be pretty sure that we have a valid parse unit */
         if (!unpack_parse_unit(&pu1, pc, pc->index - 13)                     ||
             !unpack_parse_unit(&pu, pc, pc->index - 13 - pu1.prev_pu_offset) ||
-            pu.next_pu_offset != pu1.prev_pu_offset) {
+            pu.next_pu_offset != pu1.prev_pu_offset                          ||
+            pc->index < pc->dirac_unit_size + 13LL + pu1.prev_pu_offset
+        ) {
             pc->index -= 9;
             *buf_size = next-9;
             pc->header_bytes_needed = 9;