diff --git a/booking.regn_form.inc b/booking.regn_form.inc
index 43dc5e3..9d7dd19 100644
--- a/booking.regn_form.inc
+++ b/booking.regn_form.inc
@@ -68,7 +68,7 @@ function booking_register_page()
  * based on https://www.drupal.org/node/854216
  * $string = string for search 
  */
-function _booking_ecclesia_name_autocomplete($string) {
+function _booking_ecclesia_name_autocomplete($string = "") {
   $matches = array();
   $sanitised_string = preg_replace("/[^a-zA-Z0-9\s\.']/", '', $string);
   $sanitised_string .= "%";