Index: /applications/editors/josm/plugins/slippymap/src/org/openstreetmap/josm/plugins/slippymap/SlippyMapPlugin.java
===================================================================
--- /applications/editors/josm/plugins/slippymap/src/org/openstreetmap/josm/plugins/slippymap/SlippyMapPlugin.java	(revision 12103)
+++ /applications/editors/josm/plugins/slippymap/src/org/openstreetmap/josm/plugins/slippymap/SlippyMapPlugin.java	(revision 12104)
@@ -21,7 +21,9 @@
     public void mapFrameInitialized(MapFrame oldFrame, MapFrame newFrame)
     {
-        SlippyMapLayer smlayer;
-        smlayer = new SlippyMapLayer();
-        Main.main.addLayer(smlayer);
+    	if (newFrame != null){
+	        SlippyMapLayer smlayer;
+	        smlayer = new SlippyMapLayer();
+	        Main.main.addLayer(smlayer);
+    	}
     }