Index: trunk/src/org/openstreetmap/josm/actions/SaveActionBase.java
===================================================================
--- trunk/src/org/openstreetmap/josm/actions/SaveActionBase.java	(revision 515)
+++ trunk/src/org/openstreetmap/josm/actions/SaveActionBase.java	(revision 516)
@@ -98,5 +98,5 @@
 			FileFilter ff = fc.getFileFilter();
 			if (ff instanceof ExtensionFileFilter)
-				fn = "." + ((ExtensionFileFilter)ff).defaultExtension;
+				fn += "." + ((ExtensionFileFilter)ff).defaultExtension;
 			else
 				fn += ".osm";