Index: trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSStyleSource.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSStyleSource.java	(revision 17111)
+++ trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSStyleSource.java	(revision 17112)
@@ -176,4 +176,6 @@
                         loadCanvas();
                         loadSettings();
+                    } else {
+                        rules.clear();
                     }
                 } finally {