Index: src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSStyleSource.java
===================================================================
--- src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSStyleSource.java	(revision 17083)
+++ src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSStyleSource.java	(working copy)
@@ -175,6 +175,8 @@
                     if (!metadataOnly) {
                         loadCanvas();
                         loadSettings();
+                    } else {
+                        rules.clear();
                     }
                 } finally {
                     closeSourceInputStream(in);