Index: modules/forum/forum.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/forum/forum.module,v
retrieving revision 1.497
diff -u -p -r1.497 forum.module
--- modules/forum/forum.module	2 Jun 2009 02:41:28 -0000	1.497
+++ modules/forum/forum.module	3 Jun 2009 03:39:57 -0000
@@ -991,7 +991,7 @@ function template_preprocess_forum_submi
 
 function _forum_user_last_visit($nid) {
   global $user;
-  static $history = array();
+  $history = &drupal_static(__FUNCTION__, array());
 
   if (empty($history)) {
     $result = db_query('SELECT nid, timestamp FROM {history} WHERE uid = %d', $user->uid);