Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.1214
diff -u -p -r1.1214 common.inc
--- includes/common.inc	5 Sep 2010 15:38:16 -0000	1.1214
+++ includes/common.inc	7 Sep 2010 06:20:43 -0000
@@ -5108,8 +5108,11 @@ function drupal_render(&$elements) {
   }
 
   // If #markup is not empty, set #type. This allows to specify just #markup on
-  // an element without setting #type.
-  if (!empty($elements['#markup']) && !isset($elements['#type'])) {
+  // an element without setting #type. We exclude integer zero and string with 
+  // zero otherwise they are recognized as empty.
+  if ((isset($elements['#markup']))
+      && (!empty($elements['#markup']) || ($elements['#markup'] == 0) || ($elements['#markup'] == '0'))
+      && (!isset($elements['#type']))) {
     $elements['#type'] = 'markup';
   }