diff --git a/src/com/characterforming/jrte/engine/Model.java b/src/com/characterforming/jrte/engine/Model.java
index 5812c13..45de400 100644
--- a/src/com/characterforming/jrte/engine/Model.java
+++ b/src/com/characterforming/jrte/engine/Model.java
@@ -351,7 +351,7 @@ protected int addSignal(Bytes signalName) {
 	}
 
 	protected int addTransducer(Bytes transducerName) {
-		Integer ordinal = this.transducerOrdinalMap.get(transducerName);
+		Integer ordinal = this.transducerOrdinalMap.computeIfAbsent(transducerName, absent -> null);
 		assert ordinal == null || transducerName.equals(this.transducerNameIndex[ordinal]);
 		if (ordinal == null) {
 			ordinal = this.transducerOrdinalMap.size();