--- chan_sip.c.orig	Mon Apr 11 21:05:21 2005
+++ chan_sip.c	Mon Apr 11 21:05:54 2005
@@ -7727,7 +7727,8 @@
 		if (seqno == p->pendinginvite) {
 			p->pendinginvite = 0;
 			__sip_ack(p, seqno, FLAG_RESPONSE, NULL);
-			if (!ast_strlen_zero(get_header(req, "Content-Type"))) {
+			if (!ast_strlen_zero(get_header(req, "Content-Type"))
+				&& strcasecmp(get_header(req, "Content-Length"), "0")) {
 				if (process_sdp(p, req))
 					return -1;
 			}