diff --git a/library/RAW_NS.ttcnpp b/library/RAW_NS.ttcnpp
index 58910d9..76ac0a2 100644
--- a/library/RAW_NS.ttcnpp
+++ b/library/RAW_NS.ttcnpp
@@ -169,6 +169,13 @@
 		NSCP[idx].send(t_NS_ALIVE_ACK);
 		if (not oneshot) { repeat; }
 		}
+	/* in oneshot mode, ignore any NS-UNITDATA we receive meanwhile.  This is
+	 * particularly useful when waiting for the first NS-ALIVE after SNS-CONFIG,
+	 * where there is a high chance of UNITDATA during the first Tns-test cycle
+	 * before the peer sends its first NS-ALIVE after Tns-test expiration */
+	[oneshot] NSCP[idx].receive(tr_NS_UNITDATA(?,?,?)) {
+		repeat;
+		}
 }
 
 /* Transmit BSSGP RESET for given BVCI and expect ACK */