diff --git a/lib/Doctrine/Pager/Layout.php b/lib/Doctrine/Pager/Layout.php
index d93bb76c1..8170e57d5 100644
--- a/lib/Doctrine/Pager/Layout.php
+++ b/lib/Doctrine/Pager/Layout.php
@@ -272,10 +272,12 @@ class Doctrine_Pager_Layout
      */ 
     public function addMaskReplacement($oldMask, $newMask, $asValue = false)
     {
-        $this->_maskReplacements[$oldMask] = array(
-            'newMask' => $newMask,
-            'asValue' => ($asValue === false) ? false : true
-        );
+        if (($oldMask = trim($oldMask)) != 'page_number') {
+            $this->_maskReplacements[$oldMask] = array(
+                'newMask' => $newMask,
+                'asValue' => ($asValue === false) ? false : true
+            );
+        }
     }