diff --git a/locallib.php b/locallib.php
index 9c966f1..6dfed0f 100644
--- a/locallib.php
+++ b/locallib.php
@@ -225,6 +225,7 @@ function clean_custom($filename) {
 
     $cleanfilenameuserpref = get_user_preferences('clean_filerenaming', '');
     if ((isset($cleanfilenameuserpref) && $cleanfilenameuserpref)) {
+        $filename = core_text::specialtoascii($filename);
         $filename = preg_replace('/[^A-Za-z0-9\_\-\.]/', '', $filename);
     }
     return clean_filename($filename);