diff --git a/library/IuUP_Emulation.ttcn b/library/IuUP_Emulation.ttcn
index b35602c..19c2c84 100644
--- a/library/IuUP_Emulation.ttcn
+++ b/library/IuUP_Emulation.ttcn
@@ -105,6 +105,7 @@
 		} else if (match(pdu, tr_IuUP_INIT_ACK)) {
 			if (st.cfg.active_init == true) {
 				log("IuUP INIT_ACK Received");
+				st.pending_tx_pdu := omit; /* Drop pending Init retrans */
 				st.state := ST_DATA_TRANSFER_READY;
 			} else {
 				setverdict(fail, "INIT_ACK received in PASSIVE role");
@@ -124,8 +125,12 @@
 	select (st.state) {
 		case (ST_INIT) {
 			if (st.cfg.active_init) {
-				/* send INIT */
-				pdu := valueof(ts_IuUP_INIT('160051673C01270000820000001710000100'O));
+				if (not isvalue(st.pending_tx_pdu)) {
+					/* send INIT */
+					pdu := valueof(ts_IuUP_INIT('160051673C01270000820000001710000100'O));
+					st.pending_tx_pdu := pdu;
+				} /* else: wait for INIT-ACK return ''O at the end */
+
 			} else {
 				/* wait for INIT */
 				if (isvalue(st.pending_tx_pdu)) {