--- class.tslib_menu ORG.php	Thu Oct 22 14:15:18 2009
+++ class.tslib_menu.php	Sun Nov 08 18:13:52 2009
@@ -2857,10 +2857,6 @@
 			$pid = $mount_info['mount_pid'];
 		}
 
-			// Set "&MP=" var:
-		$MP_var = implode(',',$MP_array);
-		$MP_params = $MP_var ? '&MP='.rawurlencode($MP_var) : '';
-
 			// UIDs to ban:
 		$banUidArray = $this->getBannedUids();
 
@@ -2873,6 +2869,16 @@
 
 		$menuItems = is_array($menuItemArray) ? $menuItemArray : $this->sys_page->getMenu($pid);
 		foreach($menuItems as $uid => $data)	{
+			// Translate UID to a mount page if MP overlay flag ("substitute this page") is set:
+			$MP_array_incl_ovl = $MP_array;
+			$mount_info = $this->sys_page->getMountPointInfo($uid);
+			if (is_array($mount_info) && $mount_info['overlay'])  {
+				$MP_array_incl_ovl[] = $mount_info['MPvar'];
+			}
+			// Set "&MP=" var:
+			$MP_var = implode(',',$MP_array_incl_ovl);
+			$MP_params = $MP_var ? '&MP='.rawurlencode($MP_var) : '';
+
 			$spacer = (t3lib_div::inList($this->spacerIDList,$data['doktype'])?1:0);		// if item is a spacer, $spacer is set
 			if ($this->mconf['SPC'] || !$spacer)	{	// If the spacer-function is not enabled, spacers will not enter the $menuArr
 				if (!t3lib_div::inList($this->doktypeExcludeList,$data['doktype']) && (!$data['nav_hide'] || $this->conf['includeNotInMenu']) && !t3lib_div::inArray($banUidArray,$uid))	{		// Page may not be 'not_in_menu' or 'Backend User Section' + not in banned uid's