Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.1138
diff -u -r1.1138 common.inc
--- includes/common.inc	28 Mar 2010 10:46:36 -0000	1.1138
+++ includes/common.inc	29 Mar 2010 03:00:42 -0000
@@ -5746,12 +5746,9 @@
     }
 
     if (!property_exists($object, $field)) {
-      // Skip fields that are not provided, unless we are inserting and a
-      // default value is provided by the schema.
-      if (!empty($primary_keys) || !isset($info['default'])) {
-        continue;
-      }
-      $object->$field = $info['default'];
+      // Skip fields that are not provided, default values are already known 
+      // by the database.
+      continue;
     }
 
     // Build array of fields to update or insert.