diff --git a/library/GTP_Templates.ttcn b/library/GTP_Templates.ttcn
index 44d9682..d8a43c2 100644
--- a/library/GTP_Templates.ttcn
+++ b/library/GTP_Templates.ttcn
@@ -7,6 +7,18 @@
 	import from GTP_CodecPort all;
 	import from IPCP_Types all;
 
+	/* Table 38 of 3GPP TS 29.060 */
+	type enumerated GTP_Cause {
+		GTP_CAUSE_REQUEST_IMEI			(1),
+		GTP_CAUSE_REQUEST_IMSI_AND_IMEI		(2),
+		GTP_CAUSE_NO_IDENTITY_NEDED		(3),
+		GTP_CAUSE_MS_REFUSES			(4),
+		GTP_CAUSE_MS_IS_NOT_GPRS_RESPONDING	(5),
+		/* reserved */
+		GTP_CAUSE_REQUEST_ACCEPTED		(128)
+		/* FIXME */
+	};
+
 	/* generalized GTP-C receive template */
 	template PDU_GTPC tr_GTP1C_PDU(template OCT1 msg_type, template OCT4 teid, template GTPC_PDUs pdu := ?) := {
 		/* N-PDU Number flag (PN) shall be set to '0'. A GTP-C receiver shall not return an