diff --git a/library/GTP_Emulation.ttcn b/library/GTP_Emulation.ttcn
index b67e828..4ea293c 100644
--- a/library/GTP_Emulation.ttcn
+++ b/library/GTP_Emulation.ttcn
@@ -30,8 +30,8 @@
 type record GtpEmulationCfg {
 	HostName gtpc_bind_ip,
 	PortNumber gtpc_bind_port,
-	HostName gtpu_bind_ip,
-	PortNumber gtpu_bind_port,
+	HostName gtpu_bind_ip optional,
+	PortNumber gtpu_bind_port optional,
 	boolean sgsn_role
 };
 
@@ -168,10 +168,12 @@
 						     cfg.gtpc_bind_port, {udp:={}});
 	g_gtpc_id := res.connId;
 
-	map(self:GTPU, system:GTPU);
-	res := GTP_CodecPort_CtrlFunct.f_GTPU_listen(GTPU, cfg.gtpu_bind_ip,
-						     cfg.gtpu_bind_port, {udp:={}});
-	g_gtpu_id := res.connId;
+	if (isvalue(cfg.gtpu_bind_ip) and isvalue(cfg.gtpu_bind_port)) {
+		map(self:GTPU, system:GTPU);
+		res := GTP_CodecPort_CtrlFunct.f_GTPU_listen(GTPU, cfg.gtpu_bind_ip,
+							     cfg.gtpu_bind_port, {udp:={}});
+		g_gtpu_id := res.connId;
+	}
 
 	g_restart_ctr := f_rnd_octstring(1);
 	g_c_seq_nr := f_rnd_int(65535);