diff --git a/src/sipsess/connect.c b/src/sipsess/connect.c
index 6280ed005..12d5d11a9 100644
--- a/src/sipsess/connect.c
+++ b/src/sipsess/connect.c
@@ -148,13 +148,18 @@ static void invite_resp_handler(int err, const struct sip_msg *msg, void *arg)
 	}
 	else if (msg->scode < 300) {
 
+		sess->established = true;
+
 		sess->hdrs = mem_deref(sess->hdrs);
 
 		err = sip_dialog_established(sess->dlg) ?
 				sip_dialog_update(sess->dlg, msg) :
 				sip_dialog_create(sess->dlg, msg);
-		if (err)
+		if (err) {
+			(void)sipsess_ack(sess->sock, sess->dlg, msg->cseq.num,
+				  sess->auth, sess->ctype, desc);
 			goto out;
+		}
 
 		if (sdp) {
 			if (sess->neg_state == SDP_NEG_LOCAL_OFFER) {
@@ -179,7 +184,6 @@ static void invite_resp_handler(int err, const struct sip_msg *msg, void *arg)
 		    && mbuf_get_left(desc))
 			sess->neg_state = SDP_NEG_DONE;
 
-		sess->established = true;
 		mem_deref(desc);
 
 		if (err || sess->terminated)