Index: /applications/editors/josm/plugins/validator/src/org/openstreetmap/josm/plugins/validator/tests/DuplicateWay.java
===================================================================
--- /applications/editors/josm/plugins/validator/src/org/openstreetmap/josm/plugins/validator/tests/DuplicateWay.java	(revision 22713)
+++ /applications/editors/josm/plugins/validator/src/org/openstreetmap/josm/plugins/validator/tests/DuplicateWay.java	(revision 22714)
@@ -167,6 +167,5 @@
         ways.remove(wayToKeep);
         commands.add(new DeleteCommand(ways));
-        Main.main.undoRedo.add(new SequenceCommand(tr("Delete duplicate ways"), commands));
-        return null;
+        return new SequenceCommand(tr("Delete duplicate ways"), commands);
     }