diff --git a/include/osmocom/gsm/gsup.h b/include/osmocom/gsm/gsup.h
index d966b2d27..523c15d43 100644
--- a/include/osmocom/gsm/gsup.h
+++ b/include/osmocom/gsm/gsup.h
@@ -59,6 +59,7 @@ enum osmo_gsup_iei {
 	OSMO_GSUP_AUTN_IE			= 0x25,
 	OSMO_GSUP_AUTS_IE			= 0x26,
 	OSMO_GSUP_RES_IE			= 0x27,
+	OSMO_GSUP_CN_DOMAIN_IE			= 0x28,
 };
 
 /*! GSUP message type */
@@ -97,6 +98,11 @@ enum osmo_gsup_cancel_type {
 	OSMO_GSUP_CANCEL_TYPE_WITHDRAW		= 2, /* on wire: 1 */
 };
 
+enum osmo_gsup_cn_domain {
+	OSMO_GSUP_CN_DOMAIN_PS			= 1,
+	OSMO_GSUP_CN_DOMAIN_CS			= 2,
+};
+
 /*! parsed/decoded PDP context information */
 struct osmo_gsup_pdp_info {
 	unsigned int			context_id;
@@ -132,6 +138,7 @@ struct osmo_gsup_message {
 	const uint8_t			*hlr_enc;
 	size_t				hlr_enc_len;
 	const uint8_t			*auts;
+	enum osmo_gsup_cn_domain	cn_domain;
 };
 
 int osmo_gsup_decode(const uint8_t *data, size_t data_len,
diff --git a/src/gsm/gsup.c b/src/gsm/gsup.c
index 7a439d48a..244c5fa8e 100644
--- a/src/gsm/gsup.c
+++ b/src/gsm/gsup.c
@@ -329,6 +329,10 @@ int osmo_gsup_decode(const uint8_t *const_data, size_t data_len,
 			gsup_msg->hlr_enc_len = value_len;
 			break;
 
+		case OSMO_GSUP_CN_DOMAIN_IE:
+			gsup_msg->cn_domain = *value;
+			break;
+
 		default:
 			LOGP(DLGSUP, LOGL_NOTICE,
 			     "GSUP IE type %d unknown\n", iei);
@@ -469,4 +473,9 @@ void osmo_gsup_encode(struct msgb *msg, const struct osmo_gsup_message *gsup_msg
 
 	if (gsup_msg->auts)
 		msgb_tlv_put(msg, OSMO_GSUP_AUTS_IE, 16, gsup_msg->auts);
+
+	if (gsup_msg->cn_domain) {
+		uint8_t dn = gsup_msg->cn_domain;
+		msgb_tlv_put(msg, OSMO_GSUP_CN_DOMAIN_IE, 1, &dn);
+	}
 }