diff --git a/res/res_srtp.c b/res/res_srtp.c
index e10421cbb4c8b4d2801180eece88278a87b44d47..ea129e1299d9a183df885dac695449ae73d03622 100644
--- a/res/res_srtp.c
+++ b/res/res_srtp.c
@@ -504,6 +504,12 @@ 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;