diff --git a/include/osmocom/gsm/gsup.h b/include/osmocom/gsm/gsup.h
index 6adb0bf..8384e24 100644
--- a/include/osmocom/gsm/gsup.h
+++ b/include/osmocom/gsm/gsup.h
@@ -43,6 +43,7 @@
 #include <osmocom/gsm/gsup_sms.h>
 #include <osmocom/gsm/protocol/gsm_23_003.h>
 #include <osmocom/gsm/protocol/gsm_04_08_gprs.h>
+#include <osmocom/gsm/gsm_utils.h>
 #include <osmocom/crypt/auth.h>
 
 #define OSMO_GSUP_PORT 4222
@@ -83,6 +84,7 @@
 	OSMO_GSUP_AUTS_IE			= 0x26,
 	OSMO_GSUP_RES_IE			= 0x27,
 	OSMO_GSUP_CN_DOMAIN_IE			= 0x28,
+	OSMO_GSUP_RAT_TYPES_IE			= 0x29,
 
 	OSMO_GSUP_SESSION_ID_IE			= 0x30,
 	OSMO_GSUP_SESSION_STATE_IE		= 0x31,
@@ -275,6 +277,9 @@
 	const uint8_t			*imei_enc;
 	size_t				imei_enc_len;
 	enum osmo_gsup_imei_result	imei_result;
+
+	enum osmo_rat_type		rat_types[8];
+	size_t				rat_types_len;
 };
 
 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 3d2a8e2..29cf488 100644
--- a/src/gsm/gsup.c
+++ b/src/gsm/gsup.c
@@ -282,6 +282,7 @@
 		     struct osmo_gsup_message *gsup_msg)
 {
 	int rc;
+	int i;
 	uint8_t tag;
 	/* the shift/match functions expect non-const pointers, but we'll
 	 * either copy the data or cast pointers back to const before returning
@@ -442,6 +443,16 @@
 			gsup_msg->cn_domain = *value;
 			break;
 
+		case OSMO_GSUP_RAT_TYPES_IE:
+			if (value_len > ARRAY_SIZE(gsup_msg->rat_types)) {
+				LOGP(DLGSUP, LOGL_ERROR, "nr of RAT types %zu > %zu\n", value_len, ARRAY_SIZE(gsup_msg->rat_types));
+				return -GMM_CAUSE_COND_IE_ERR;
+			}
+			for (i = 0; i < value_len; i++)
+				gsup_msg->rat_types[i] = value[i];
+			gsup_msg->rat_types_len = value_len;
+			break;
+
 		case OSMO_GSUP_CHARG_CHAR_IE:
 			gsup_msg->pdp_charg_enc = value;
 			gsup_msg->pdp_charg_enc_len = value_len;
@@ -676,6 +687,20 @@
 		msgb_tlv_put(msg, OSMO_GSUP_CN_DOMAIN_IE, 1, &dn);
 	}
 
+	if (gsup_msg->rat_types_len) {
+		int i;
+		uint8_t *len = msgb_tl_put(msg, OSMO_GSUP_RAT_TYPES_IE);
+		*len = gsup_msg->rat_types_len;
+		for (i = 0; i < gsup_msg->rat_types_len; i++) {
+			if (!gsup_msg->rat_types[i] || gsup_msg->rat_types[i] >= OSMO_RAT_COUNT) {
+				LOGP(DLGSUP, LOGL_ERROR, "Failed to encode RAT type %s (nr %d)\n",
+				     osmo_rat_type_name(gsup_msg->rat_types[i]), i);
+				return -EINVAL;
+			}
+			msgb_v_put(msg, gsup_msg->rat_types[i]);
+		}
+	}
+
 	if (gsup_msg->pdp_charg_enc) {
 		msgb_tlv_put(msg, OSMO_GSUP_CHARG_CHAR_IE,
 				gsup_msg->pdp_charg_enc_len, gsup_msg->pdp_charg_enc);
diff --git a/tests/gsup/gsup_test.err b/tests/gsup/gsup_test.err
index 73b35fc..ea6fa15 100644
--- a/tests/gsup/gsup_test.err
+++ b/tests/gsup/gsup_test.err
@@ -101,26 +101,26 @@
 DLGSUP Stopping DLGSUP logging
   message 0: tested 2816 modifications, 510 parse failures
   message 1: tested 3584 modifications, 770 parse failures
-  message 2: tested 21248 modifications, 2575 parse failures
+  message 2: tested 21248 modifications, 2577 parse failures
   message 3: tested 2816 modifications, 510 parse failures
   message 4: tested 3584 modifications, 770 parse failures
-  message 5: tested 20736 modifications, 4022 parse failures
+  message 5: tested 20736 modifications, 4024 parse failures
   message 6: tested 3584 modifications, 771 parse failures
   message 7: tested 3584 modifications, 770 parse failures
   message 8: tested 2816 modifications, 510 parse failures
   message 9: tested 2816 modifications, 510 parse failures
   message 10: tested 3584 modifications, 770 parse failures
   message 11: tested 3328 modifications, 769 parse failures
-  message 12: tested 54016 modifications, 4626 parse failures
-  message 13: tested 11520 modifications, 1026 parse failures
+  message 12: tested 54016 modifications, 4628 parse failures
+  message 13: tested 11520 modifications, 1028 parse failures
   message 14: tested 5120 modifications, 1030 parse failures
-  message 15: tested 10752 modifications, 1262 parse failures
+  message 15: tested 10752 modifications, 1263 parse failures
   message 16: tested 7680 modifications, 1271 parse failures
   message 17: tested 8448 modifications, 2053 parse failures
-  message 18: tested 11264 modifications, 2307 parse failures
+  message 18: tested 11264 modifications, 2308 parse failures
   message 19: tested 5120 modifications, 1031 parse failures
   message 20: tested 6656 modifications, 1546 parse failures
   message 21: tested 3584 modifications, 771 parse failures
-  message 22: tested 5632 modifications, 771 parse failures
+  message 22: tested 5632 modifications, 772 parse failures
   message 23: tested 3584 modifications, 770 parse failures
   message 24: tested 3584 modifications, 771 parse failures