diff --git a/libavformat/sdp.c b/libavformat/sdp.c
index 2ce1a62262..5343e8d1d3 100644
--- a/libavformat/sdp.c
+++ b/libavformat/sdp.c
@@ -195,6 +195,8 @@ static char *extradata2psets(AVFormatContext *s, AVCodecParameters *par)
             continue;
         }
         if (p != (psets + strlen(pset_string))) {
+            if (p - psets >= MAX_PSET_SIZE)
+                goto fail_in_loop;
             *p = ',';
             p++;
         }
@@ -204,6 +206,7 @@ static char *extradata2psets(AVFormatContext *s, AVCodecParameters *par)
         }
         if (!av_base64_encode(p, MAX_PSET_SIZE - (p - psets), r, r1 - r)) {
             av_log(s, AV_LOG_ERROR, "Cannot Base64-encode %"PTRDIFF_SPECIFIER" %"PTRDIFF_SPECIFIER"!\n", MAX_PSET_SIZE - (p - psets), r1 - r);
+fail_in_loop:
             av_free(psets);
             av_free(tmpbuf);