Index: trunk/resources/data/validator/numeric.mapcss
===================================================================
--- trunk/resources/data/validator/numeric.mapcss	(revision 17937)
+++ trunk/resources/data/validator/numeric.mapcss	(revision 17939)
@@ -63,5 +63,6 @@
   assertNoMatch: "node level=-1;-0.5";
   assertNoMatch: "node building:levels=1.5";
-  assertMatch: "node building:levels=-1";
+  assertNoMatch: "node building:levels=-1"; /* tested already by rule above "negative values" and excluded here via !.negative_value in selector */
+  assertMatch: "node building:levels=1A";
   assertNoMatch: "node building:levels=0"; /* valid because there can be building:levels:underground > 0 or roof:levels > 0 */
 }