diff --git a/include/osmocom/gsm/gsm0808.h b/include/osmocom/gsm/gsm0808.h
index 38d88ef..5380dd9 100644
--- a/include/osmocom/gsm/gsm0808.h
+++ b/include/osmocom/gsm/gsm0808.h
@@ -30,7 +30,8 @@
 struct msgb *gsm0808_create_clear_complete(void);
 struct msgb *gsm0808_create_cipher_complete(struct msgb *layer3, uint8_t alg_id);
 struct msgb *gsm0808_create_cipher_reject(uint8_t cause);
-struct msgb *gsm0808_create_classmark_update(const uint8_t *classmark, uint8_t length);
+struct msgb *gsm0808_create_classmark_update(const uint8_t *cm2, uint8_t cm2_len,
+					     const uint8_t *cm3, uint8_t cm3_len);
 struct msgb *gsm0808_create_sapi_reject(uint8_t link_id);
 struct msgb *gsm0808_create_assignment_completed(uint8_t rr_cause,
 						 uint8_t chosen_channel, uint8_t encr_alg_id,
diff --git a/src/gsm/gsm0808.c b/src/gsm/gsm0808.c
index 6c10177..3009827 100644
--- a/src/gsm/gsm0808.c
+++ b/src/gsm/gsm0808.c
@@ -143,7 +143,8 @@
 	return msg;
 }
 
-struct msgb *gsm0808_create_classmark_update(const uint8_t *classmark_data, uint8_t length)
+struct msgb *gsm0808_create_classmark_update(const uint8_t *cm2, uint8_t cm2_len,
+					     const uint8_t *cm3, uint8_t cm3_len)
 {
 	struct msgb *msg = msgb_alloc_headroom(BSSMAP_MSG_SIZE, BSSMAP_MSG_HEADROOM,
 					       "classmark-update");
@@ -151,8 +152,10 @@
 		return NULL;
 
 	msgb_v_put(msg, BSS_MAP_MSG_CLASSMARK_UPDATE);
-	msg->l4h = msgb_put(msg, length);
-	memcpy(msg->l4h, classmark_data, length);
+	msgb_tlv_put(msg, GSM0808_IE_CLASSMARK_INFORMATION_T2, cm2_len, cm2);
+	if (cm3)
+		msgb_tlv_put(msg, GSM0808_IE_CLASSMARK_INFORMATION_T3,
+			     cm3_len, cm3);
 
 	msg->l3h = msgb_tv_push(msg, BSSAP_MSG_BSS_MANAGEMENT, msgb_length(msg));
 
diff --git a/tests/gsm0808/gsm0808_test.c b/tests/gsm0808/gsm0808_test.c
index 50838c8..7e5e97b 100644
--- a/tests/gsm0808/gsm0808_test.c
+++ b/tests/gsm0808/gsm0808_test.c
@@ -136,13 +136,21 @@
 
 static void test_create_cm_u()
 {
-	static const uint8_t res[] = { 0x00, 0x02, 0x54, 0x23 };
+	static const uint8_t res[] = {
+		0x00, 0x07, 0x54, 0x12, 0x01, 0x23, 0x13, 0x01, 0x42 };
+	static const uint8_t res2o[] = {
+		0x00, 0x04, 0x54, 0x12, 0x01, 0x23 };
 	struct msgb *msg;
-	const uint8_t cm = 0x23;
+	const uint8_t cm2 = 0x23;
+	const uint8_t cm3 = 0x42;
 
 	printf("Testing creating CM U\n");
-	msg = gsm0808_create_classmark_update(&cm, 1);
+	msg = gsm0808_create_classmark_update(&cm2, 1, &cm3, 1);
 	VERIFY(msg, res, ARRAY_SIZE(res));
+
+	msg = gsm0808_create_classmark_update(&cm2, 1, NULL, 0);
+	VERIFY(msg, res2o, ARRAY_SIZE(res2o));
+
 	msgb_free(msg);
 }