Index: trunk/src/org/openstreetmap/josm/gui/preferences/imagery/AddWMSLayerPanel.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/preferences/imagery/AddWMSLayerPanel.java	(revision 17548)
+++ trunk/src/org/openstreetmap/josm/gui/preferences/imagery/AddWMSLayerPanel.java	(revision 17552)
@@ -207,5 +207,10 @@
             return false;
         }
-        if (setDefaultLayers.isSelected() && (tree == null || tree.getSelectedLayers().isEmpty())) {
+        /*
+         * We need selection of the layers in following situations:
+         * * endpoint is not selected (and we don't care about setDefault layers as it's disabled anyway)
+         * * endpoint is selected and setDefultLayers is selected
+         */
+        if ((!endpoint.isSelected() || setDefaultLayers.isSelected()) && (tree == null || tree.getSelectedLayers().isEmpty())) {
             return false;
         }