--- duplicate.module
+++ (clipboard)
@@ -63,7 +63,7 @@
  * The arg() function may not be availble early in the bootstrap process,
  * so we reimplement it here.
  */
-function _duplicate_arg() {
+function _duplicate_arg($index = NULL) {
   static $arguments, $q;
 
   if (empty($arguments) || $q != $_GET['q']) {