Index: /trunk/resources/data/validator/deprecated.mapcss
===================================================================
--- /trunk/resources/data/validator/deprecated.mapcss	(revision 18187)
+++ /trunk/resources/data/validator/deprecated.mapcss	(revision 18188)
@@ -504,11 +504,15 @@
 }
 
-/* #10837 */
+/* #10837, #21268 */
 *[building][levels],
-*[building:part=yes][levels] {
+*[building:part][levels] {
   throwWarning: tr("{0} is deprecated", "{1.key}");
   suggestAlternative: "building:levels";
   group: tr("deprecated tagging");
   fixChangeKey: "levels => building:levels";
+  set levels_building;
+}
+*[levels]!.levels_building {
+  throwWarning: tr("Unusual key {0}, maybe {1} or {2} is meant", "{0.key}", "level", "building:levels");
 }
 
Index: /trunk/resources/data/validator/ignoretags.cfg
===================================================================
--- /trunk/resources/data/validator/ignoretags.cfg	(revision 18187)
+++ /trunk/resources/data/validator/ignoretags.cfg	(revision 18188)
@@ -703,4 +703,5 @@
 K:landuse=school
 E:role
+E:levels
 ;
 ; Tags not yet decided (to remove from this section when added or moved up when deprecated)