diff --git a/private_number.module b/private_number.module
index de77281..9231eb2 100644
--- a/private_number.module
+++ b/private_number.module
@@ -303,7 +303,7 @@ function private_number_process($element, $edit, $form_state, $form) {
  * $element['#field_name'] contains the field name
  * $element['#delta]  is the position of this element in the group
  */
-function theme_private_number(&$element) {
+function theme_private_number($element) {
   return $element['#children'];
 }