diff --git a/include/osmocom/ranap/ranap_msg_factory.h b/include/osmocom/ranap/ranap_msg_factory.h
index 96398814..120c6e6b 100644
--- a/include/osmocom/ranap/ranap_msg_factory.h
+++ b/include/osmocom/ranap/ranap_msg_factory.h
@@ -32,7 +32,9 @@ struct msgb *ranap_new_msg_iu_rel_compl(void);
 struct msgb *ranap_new_msg_paging_cmd(const char *imsi, const uint32_t *tmsi, int is_ps, uint32_t cause);
 
 /*! \brief generate RANAP RAB ASSIGNMENT REQUEST message for CS (voice) */
-struct msgb *ranap_new_msg_rab_assign_voice(uint8_t rab_id, uint32_t rtp_ip, uint16_t rtp_port);
+struct msgb *ranap_new_msg_rab_assign_voice(uint8_t rab_id, uint32_t rtp_ip,
+					    uint16_t rtp_port,
+					    bool use_x213_nsap);
 
 /*! \brief generate RANAP RAB ASSIGNMENT REQUEST message for PS (data) */
 struct msgb *ranap_new_msg_rab_assign_data(uint8_t rab_id, uint32_t gtp_ip,
diff --git a/src/ranap_msg_factory.c b/src/ranap_msg_factory.c
index 401ef4ed..695a6be1 100644
--- a/src/ranap_msg_factory.c
+++ b/src/ranap_msg_factory.c
@@ -647,7 +647,8 @@ static void new_transp_layer_addr(BIT_STRING_t *out, uint32_t ip, bool use_x213_
 	out->bits_unused = 0;
 }
 
-static RANAP_TransportLayerInformation_t *new_transp_info_rtp(uint32_t ip, uint16_t port)
+static RANAP_TransportLayerInformation_t *new_transp_info_rtp(uint32_t ip, uint16_t port,
+							      bool use_x213_nsap)
 {
 	RANAP_TransportLayerInformation_t *tli = CALLOC(1, sizeof(*tli));
 	uint8_t binding_id[4];
@@ -661,7 +662,7 @@ static RANAP_TransportLayerInformation_t *new_transp_info_rtp(uint32_t ip, uint1
 	binding_id[3] = 1;
 #endif
 
-	new_transp_layer_addr(&tli->transportLayerAddress, ip, 1);
+	new_transp_layer_addr(&tli->transportLayerAddress, ip, use_x213_nsap);
 	tli->iuTransportAssociation.present = RANAP_IuTransportAssociation_PR_bindingID;
 	OCTET_STRING_fromBuf(&tli->iuTransportAssociation.choice.bindingID,
 				(const char *) binding_id, sizeof(binding_id));
@@ -710,7 +711,9 @@ static void assign_new_ra_id(RANAP_RAB_ID_t *id, uint8_t rab_id)
 }
 
 /*! \brief generate RANAP RAB ASSIGNMENT REQUEST message for CS (voice) */
-struct msgb *ranap_new_msg_rab_assign_voice(uint8_t rab_id, uint32_t rtp_ip, uint16_t rtp_port)
+struct msgb *ranap_new_msg_rab_assign_voice(uint8_t rab_id, uint32_t rtp_ip,
+					    uint16_t rtp_port,
+					    bool use_x213_nsap)
 {
 	RANAP_ProtocolIE_FieldPair_t *pair;
 	RANAP_RAB_AssignmentRequestIEs_t ies;
@@ -731,7 +734,8 @@ struct msgb *ranap_new_msg_rab_assign_voice(uint8_t rab_id, uint32_t rtp_ip, uin
 	//first.nAS_SynchronisationIndicator = FIXME;
 	first.rAB_Parameters = new_rab_par_voice();
 	first.userPlaneInformation = new_upi(RANAP_UserPlaneMode_support_mode_for_predefined_SDU_sizes, 1); /* 2? */
-	first.transportLayerInformation = new_transp_info_rtp(rtp_ip, rtp_port);
+	first.transportLayerInformation = new_transp_info_rtp(rtp_ip, rtp_port,
+							      use_x213_nsap);
 
 	/* put together the 'Second' part */
 	RANAP_RAB_SetupOrModifyItemSecond_t second;
diff --git a/src/tests/test-ranap.c b/src/tests/test-ranap.c
index 7b1f3bf5..ce01b968 100644
--- a/src/tests/test-ranap.c
+++ b/src/tests/test-ranap.c
@@ -148,7 +148,7 @@ int main(int argc, char **argv)
 		msgb_free(msg);
 
 		printf("\n==> RAB ASSIGNMENT COMMAND (VOICE)\n");
-		msg = ranap_new_msg_rab_assign_voice(1, rtp_ip, rtp_port);
+		msg = ranap_new_msg_rab_assign_voice(1, rtp_ip, rtp_port, 1);
 		if (msg)
 			printf("%s\n", msgb_hexdump(msg));
 		msgb_free(msg);