Index: trunk/resources/data/validator/geometry.mapcss
===================================================================
--- trunk/resources/data/validator/geometry.mapcss	(revision 17933)
+++ trunk/resources/data/validator/geometry.mapcss	(revision 17957)
@@ -138,4 +138,10 @@
 way:closed[power=line] {
   throwWarning: tr("{0} on a closed way. Should be used on an unclosed way.", "{1.tag}"); 
+}
+
+/* #20902 */
+relation[area?] {
+  throwWarning: tr("{0} on a relation", "{0.key}");
+  fixRemove: "{0.key}";
 }