Index: /trunk/src/org/openstreetmap/josm/command/AddCommand.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/command/AddCommand.java	(revision 11139)
+++ /trunk/src/org/openstreetmap/josm/command/AddCommand.java	(revision 11140)
@@ -37,5 +37,5 @@
      */
     public AddCommand(OsmPrimitive osm) {
-        this.osm = osm;
+        this.osm = Objects.requireNonNull(osm, "osm");
     }
 
@@ -47,5 +47,5 @@
     public AddCommand(OsmDataLayer layer, OsmPrimitive osm) {
         super(layer);
-        this.osm = osm;
+        this.osm = Objects.requireNonNull(osm, "osm");
     }