Index: trunk/data/validator/deprecated.mapcss
===================================================================
--- trunk/data/validator/deprecated.mapcss	(revision 13049)
+++ trunk/data/validator/deprecated.mapcss	(revision 13218)
@@ -1164,2 +1164,10 @@
   group: tr("deprecated tagging");
 }
+
+way[building=y],
+way[building=1] {
+  throwError: tr("{0}", "{0.tag}");
+  suggestAlternative: "building=yes";
+  group: tr("misspelled value");
+  fixAdd: "building=yes";
+}