diff --git a/include/gsup_protocol.hrl b/include/gsup_protocol.hrl
index 1c755ac..d30f12c 100644
--- a/include/gsup_protocol.hrl
+++ b/include/gsup_protocol.hrl
@@ -8,6 +8,20 @@
 -ifndef(GSUP_PROTOCOL).
 -define(GSUP_PROTOCOL, true).
 
+% TS 24.008 10.5.5.14, GMM Cause used in GSUP:
+-define(GSUP_CAUSE_IMSI_UNKNOWN,			16#02).
+-define(GSUP_CAUSE_ILLEGAL_MS,				16#03).
+-define(GSUP_CAUSE_GPRS_NOTALLOWED,		16#07).
+-define(GSUP_CAUSE_PLMN_NOTALLOWED,		16#0b).
+-define(GSUP_CAUSE_LA_NOTALLOWED,			16#0c).
+-define(GSUP_CAUSE_ROAMING_NOTALLOWED,	16#0d).
+-define(GSUP_CAUSE_NO_SUIT_CELL_IN_LA,	16#0f).
+-define(GSUP_CAUSE_NET_FAIL,					16#11).
+-define(GSUP_CAUSE_CONGESTION,				16#16).
+-define(GSUP_CAUSE_GSM_AUTH_UNACCEPT,	16#17).
+-define(GSUP_CAUSE_INV_MAND_INFO,			16#60).
+-define(GSUP_CAUSE_PROTO_ERR_UNSPEC,	16#6f).
+
 -type 'GSUPMessageType'() :: location_upd_req
                   | location_upd_err
                   | location_upd_res