Index: trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/Condition.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/Condition.java	(revision 8251)
+++ trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/Condition.java	(revision 8252)
@@ -414,4 +414,5 @@
             case "unclosed_multipolygon":
                 return e.osm instanceof Relation && ((Relation) e.osm).isMultipolygon() &&
+                        !e.osm.isIncomplete() && !((Relation) e.osm).hasIncompleteMembers() &&
                         !MultipolygonCache.getInstance().get(Main.map.mapView, (Relation) e.osm).getOpenEnds().isEmpty();
             case "open_end":