--- channels/chan_sip.c.orig	2009-11-30 15:51:28.000000000 -0500
+++ channels/chan_sip.c	2009-12-01 14:58:57.000000000 -0500
@@ -5941,8 +5941,12 @@
 		res = -1; /* Tell Asterisk to generate inband indications */
 		break;
 	case SIP_DTMF_RFC2833:
-		if (p->rtp)
+		if (p->rtp) {
+			if (ast_test_flag(&p->flags[1], SIP_PAGE2_CONSTANT_SSRC)) {
+                                        ast_rtp_set_constantssrc(p->rtp);
+			}	
 			ast_rtp_senddigit_begin(p->rtp, digit);
+		}
 		break;
 	default:
 		break;