diff --git a/include/osmocom/msc/transaction.h b/include/osmocom/msc/transaction.h
index 36e9bc1..c5c740c 100644
--- a/include/osmocom/msc/transaction.h
+++ b/include/osmocom/msc/transaction.h
@@ -111,7 +111,7 @@
 void trans_free(struct gsm_trans *trans);
 
 int trans_assign_trans_id(const struct gsm_network *net, const struct vlr_subscr *vsub,
-			  uint8_t protocol, uint8_t ti_flag);
+			  uint8_t protocol);
 struct gsm_trans *trans_has_conn(const struct ran_conn *conn);
 void trans_conn_closed(const struct ran_conn *conn);
 
diff --git a/src/libmsc/gsm_04_08_cc.c b/src/libmsc/gsm_04_08_cc.c
index 93e136c..b84fd03 100644
--- a/src/libmsc/gsm_04_08_cc.c
+++ b/src/libmsc/gsm_04_08_cc.c
@@ -630,8 +630,7 @@
 	}
 
 	/* Get free transaction_id */
-	trans_id = trans_assign_trans_id(trans->net, trans->vsub,
-					 GSM48_PDISC_CC, 0);
+	trans_id = trans_assign_trans_id(trans->net, trans->vsub, GSM48_PDISC_CC);
 	if (trans_id < 0) {
 		/* no free transaction ID */
 		rc = mncc_release_ind(trans->net, trans, trans->callref,
diff --git a/src/libmsc/gsm_04_11.c b/src/libmsc/gsm_04_11.c
index e63d1b6..ccb2610 100644
--- a/src/libmsc/gsm_04_11.c
+++ b/src/libmsc/gsm_04_11.c
@@ -1064,7 +1064,7 @@
 	LOGP(DLSMS, LOGL_INFO, "Going to send a MT SMS\n");
 
 	/* Generate a new transaction ID */
-	tid = trans_assign_trans_id(net, vsub, GSM48_PDISC_SMS, 0);
+	tid = trans_assign_trans_id(net, vsub, GSM48_PDISC_SMS);
 	if (tid == -1) {
 		LOGP(DLSMS, LOGL_ERROR, "No available transaction IDs\n");
 		return NULL;
diff --git a/src/libmsc/gsm_09_11.c b/src/libmsc/gsm_09_11.c
index dca315d..08721d4 100644
--- a/src/libmsc/gsm_09_11.c
+++ b/src/libmsc/gsm_09_11.c
@@ -306,8 +306,7 @@
 	osmo_counter_inc(net->active_nc_ss);
 
 	/* Assign transaction ID */
-	tid = trans_assign_trans_id(trans->net,
-		trans->vsub, GSM48_PDISC_NC_SS, 0);
+	tid = trans_assign_trans_id(trans->net, trans->vsub, GSM48_PDISC_NC_SS);
 	if (tid < 0) {
 		LOGP(DMM, LOGL_ERROR, "No free transaction ID\n");
 		/* TODO: inform HLR about this */
diff --git a/src/libmsc/transaction.c b/src/libmsc/transaction.c
index 7c91c92..237191d 100644
--- a/src/libmsc/transaction.c
+++ b/src/libmsc/transaction.c
@@ -179,22 +179,19 @@
 }
 
 /*! allocate an unused transaction ID for the given subscriber
- * in the given protocol using the ti_flag specified
+ * in the given protocol using TI flag = 0 (allocated by us).
+ * See GSM 04.07, section 11.2.3.1.3 "Transaction identifier".
  * \param[in] net GSM network
  * \param[in] subscr Subscriber for which to find ID
  * \param[in] protocol Protocol for whihc to find ID
- * \param[in] ti_flag FIXME
  */
 int trans_assign_trans_id(const struct gsm_network *net, const struct vlr_subscr *vsub,
-			  uint8_t protocol, uint8_t ti_flag)
+			  uint8_t protocol)
 {
 	struct gsm_trans *trans;
 	unsigned int used_tid_bitmask = 0;
 	int i, j, h;
 
-	if (ti_flag)
-		ti_flag = 0x8;
-
 	/* generate bitmask of already-used TIDs for this (subscr,proto) */
 	llist_for_each_entry(trans, &net->trans_list, entry) {
 		if (trans->vsub != vsub ||
@@ -206,10 +203,10 @@
 
 	/* find a new one, trying to go in a 'circular' pattern */
 	for (h = 6; h > 0; h--)
-		if (used_tid_bitmask & (1 << (h | ti_flag)))
+		if (used_tid_bitmask & (1 << h))
 			break;
 	for (i = 0; i < 7; i++) {
-		j = ((h + i) % 7) | ti_flag;
+		j = (h + i) % 7;
 		if ((used_tid_bitmask & (1 << j)) == 0)
 			return j;
 	}