Index: trunk/resources/data/validator/wikipedia.mapcss
===================================================================
--- trunk/resources/data/validator/wikipedia.mapcss	(revision 16006)
+++ trunk/resources/data/validator/wikipedia.mapcss	(revision 16861)
@@ -145,4 +145,19 @@
 }
 
+/* Detect wikidata value wrongly in wikipedia key, not 100% safe as there might be wikipedia articles matching the regexp, therefore no fixChangeKey */
+*[wikipedia][wikipedia =~ /^[-a-zA-Z]{2,12}:Q[1-9][0-9]{0,8}$/] {
+  throwWarning: tr("{0} value looks like a {1} value", "{0.key}", "wikidata");
+  assertNoMatch: "node wikipedia=a";
+  assertNoMatch: "node wikipedia=de:a";
+  assertNoMatch: "node wikipedia=de:Q";
+  assertNoMatch: "node wikipedia=de:Q0";
+  assertNoMatch: "node wikipedia=de:Q0123";
+  assertNoMatch: "node wikipedia=en-GB:Q0123";
+  assertMatch: "node wikipedia=de:Q123";
+  assertMatch: "node wikipedia=de:Q1";
+  assertMatch: "node wikipedia=en-GB:Q123";
+  assertMatch: "node wikipedia=en-GB:Q1";
+}
+
 /* Wikipedia:lang without wikipedia */
 *[!wikipedia][/^wikipedia:/] {