--- modules/diff/diff.moduleold	Wed Jun 20 09:52:22 2007
+++ modules/diff/diff.module	Wed Jun 20 10:07:28 2007
@@ -421,7 +421,12 @@ function diff_form_alter($form_id, &$for
       // Change the form render callback to display the new button
       $form['#theme'] = 'diff_node_form';
       // Hijack the callback to handle showing of the diff if requested.
-      $form['#after_build'] = array('diff_node_form_add_changes');
+      if (isset($form['#after_build']) && is_array($form['#after_build'])) {
+        array_push($form['#after_build'], 'diff_node_form_add_changes');
+      }
+      else {
+        $form['#after_build'] = array('diff_node_form_add_changes');
+      }
     }
   }  
 }