Index: trunk/src/org/openstreetmap/josm/data/validation/tests/MapCSSTagCheckerRule.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/validation/tests/MapCSSTagCheckerRule.java	(revision 19272)
+++ trunk/src/org/openstreetmap/josm/data/validation/tests/MapCSSTagCheckerRule.java	(revision 19273)
@@ -151,7 +151,7 @@
                     } else if (val != null && "suggestAlternative".equals(ai.key)) {
                         check.alternatives.add(val);
-                    } else if (val != null && "assertMatch".equals(ai.key)) {
+                    } else if (val != null && "assertMatch".equals(ai.key) && !assertions.containsKey(val)) {
                         assertions.put(val, Boolean.TRUE);
-                    } else if (val != null && "assertNoMatch".equals(ai.key)) {
+                    } else if (val != null && "assertNoMatch".equals(ai.key) && !assertions.containsKey(val)) {
                         assertions.put(val, Boolean.FALSE);
                     } else if (val != null && "group".equals(ai.key)) {