diff --git a/workflow/engine/methods/login/authentication.php b/workflow/engine/methods/login/authentication.php
index a233c0074..8cee44235 100755
--- a/workflow/engine/methods/login/authentication.php
+++ b/workflow/engine/methods/login/authentication.php
@@ -36,7 +36,7 @@ try {
         $pwd = '';
 
         if (isset($frm['USR_USERNAME'])) {
-            $usr = strtolower(trim($frm['USR_USERNAME']));
+            $usr = mb_strtolower(trim($frm['USR_USERNAME']), 'UTF-8');
             $pwd = trim($frm['USR_PASSWORD']);
         }