Index: src/org/openstreetmap/josm/gui/dialogs/relation/RelationEditor.java
===================================================================
--- src/org/openstreetmap/josm/gui/dialogs/relation/RelationEditor.java	(Revision 1869)
+++ src/org/openstreetmap/josm/gui/dialogs/relation/RelationEditor.java	(Arbeitskopie)
@@ -105,7 +105,7 @@
                 false
         );
         if (layer == null)
-            throw new IllegalArgumentException(tr("parameter ''layer'' must not be null", "layer"));
+            throw new IllegalArgumentException(tr("parameter ''{0}'' must not be null", "layer"));
         this.layer = layer;
         setRelation(relation);
     }