diff --git a/libavformat/rtpenc.c b/libavformat/rtpenc.c
index 26f89cd7af..d2a8646a95 100644
--- a/libavformat/rtpenc.c
+++ b/libavformat/rtpenc.c
@@ -269,6 +269,7 @@ static int rtp_write_header(AVFormatContext *s1)
             ret = AVERROR_EXPERIMENTAL;
             goto fail;
         }
+        payload_header_size = 1;
         break;
     case AV_CODEC_ID_AV1:
         if (s1->strict_std_compliance > FF_COMPLIANCE_EXPERIMENTAL) {