diff --git a/res/res_srtp.c b/res/res_srtp.c
index 3519def7ed267a073536e1ae00a6e98e1fdbaf8e..c73d9b2ef22a1417e6193a4c13fd6f2238ab952d 100644
--- a/res/res_srtp.c
+++ b/res/res_srtp.c
@@ -502,6 +502,12 @@ static int ast_srtp_protect(struct ast_srtp *srtp, void **buf, int *len, int rtc
 
 	memcpy(localbuf, *buf, *len);
 
+	if(rtcp){
+		// align ssrc with length of 32bits.
+		memcpy(localbuf+4, srtp->buf+8, 4);
+		memcpy(srtp->rtcpbuf+4, srtp->buf+8, 4);
+	}
+
 	if ((res = rtcp ? srtp_protect_rtcp(srtp->session, localbuf, len) : srtp_protect(srtp->session, localbuf, len)) != err_status_ok && res != err_status_replay_fail) {
 		ast_log(LOG_WARNING, "SRTP protect: %s\n", srtp_errstr(res));
 		return -1;