Index: /trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/ConditionFactory.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/ConditionFactory.java	(revision 17798)
+++ /trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/ConditionFactory.java	(revision 17799)
@@ -645,5 +645,6 @@
         @Override
         public boolean applies(Tagged osm) {
-            return osm.keys().anyMatch(pattern.asPredicate()) ^ negateResult;
+            boolean matches = osm.hasKeys() && osm.keys().anyMatch(pattern.asPredicate());
+            return matches ^ negateResult;
         }