--- search_api_db/service.inc	Sun Jul 01 14:47:47 2012
+++ search_api_db/service.inc	Tue Dec 11 17:44:40 2012
@@ -1125,7 +1125,7 @@
         // table for "missing" entries. Therefore, we have to exclude NULL
         // values if we do not want a "missing" facet.
         else {
-          $select->isNotNull('value');
+          $select->isNotNull(search_api_is_text_type($field['type']) ? 'word' : 'value');
         }
       }