diff --git a/src/main/java/de/tla2b/types/StructOrFunctionType.java b/src/main/java/de/tla2b/types/StructOrFunctionType.java
index d32b8f871834291ac00f1ac27b87b3ca89c4b3bd..7ac9f52e138a6fc0b7a2dfd992517bbb61eb57f8 100644
--- a/src/main/java/de/tla2b/types/StructOrFunctionType.java
+++ b/src/main/java/de/tla2b/types/StructOrFunctionType.java
@@ -186,7 +186,7 @@ public class StructOrFunctionType extends AbstractHasFollowers {
 
 	@Override
 	public PExpression getBNode() {
-		return null;
+		throw new UnsupportedOperationException("StructOrFunctionType has no corresponding B node.");
 	}
 
 	public void apply(TypeVisitorInterface visitor) {