diff --git a/data/web/sogo-auth.php b/data/web/sogo-auth.php
index af6f851b..d1552710 100644
--- a/data/web/sogo-auth.php
+++ b/data/web/sogo-auth.php
@@ -11,6 +11,7 @@ $session_var_pass = 'sogo-sso-pass';
 // validate credentials for basic auth requests
 if (isset($_SERVER['PHP_AUTH_USER'])) {
   // load prerequisites only when required
+  require_once $_SERVER['DOCUMENT_ROOT'] . '/inc/prerequisites.inc.php';
   require_once $_SERVER['DOCUMENT_ROOT'] . '/inc/functions.inc.php';
   require_once $_SERVER['DOCUMENT_ROOT'] . '/inc/functions.auth.inc.php';
   $username = $_SERVER['PHP_AUTH_USER'];