Index: trunk/test/unit/org/openstreetmap/josm/data/validation/tests/MapCSSTagCheckerTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/data/validation/tests/MapCSSTagCheckerTest.java	(revision 13194)
+++ trunk/test/unit/org/openstreetmap/josm/data/validation/tests/MapCSSTagCheckerTest.java	(revision 13195)
@@ -263,3 +263,15 @@
         doTestNaturalWood(14289, "example2.osm", 3, 3);
     }
+
+    /**
+     * Non-regression test for <a href="https://josm.openstreetmap.de/ticket/15641">Bug #15641</a>.
+     * @throws ParseException if an error occurs
+     */
+    @Test
+    public void testTicket15641() throws ParseException {
+        assertNotNull(buildTagChecker(
+                "relation[type=public_transport][public_transport=stop_area_group] > way {" +
+                "  throwWarning: eval(count(parent_tags(public_transport)));" +
+                "}"));
+    }
 }