Index: /trunk/src/org/openstreetmap/josm/gui/MapView.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/MapView.java	(revision 6566)
+++ /trunk/src/org/openstreetmap/josm/gui/MapView.java	(revision 6567)
@@ -736,6 +736,6 @@
      * @return an unmodifiable list of layers of a certain type.
      */
-    public <T extends Layer> Collection<T>  getLayersOfType(Class<T> ofType) {
-        return Utils.filteredCollection(getAllLayers(), ofType);
+    public <T extends Layer> List<T>  getLayersOfType(Class<T> ofType) {
+        return new ArrayList<T>(Utils.filteredCollection(getAllLayers(), ofType));
     }