Index: applications/viewer/jmapviewer/src/org/openstreetmap/gui/jmapviewer/OsmTileSource.java
===================================================================
--- applications/viewer/jmapviewer/src/org/openstreetmap/gui/jmapviewer/OsmTileSource.java	(revision 18286)
+++ applications/viewer/jmapviewer/src/org/openstreetmap/gui/jmapviewer/OsmTileSource.java	(revision 18356)
@@ -29,6 +29,10 @@
         }
 
+        public String getExtension() {
+            return "png";
+        }
+
         public String getTilePath(int zoom, int tilex, int tiley) {
-            return "/" + zoom + "/" + tilex + "/" + tiley + ".png";
+            return "/" + zoom + "/" + tilex + "/" + tiley + "." + getExtension();
         }