diff --git a/auth/ldap/lib.php b/auth/ldap/lib.php
index 77fa8f2..aa55b8a 100644
--- a/auth/ldap/lib.php
+++ b/auth/ldap/lib.php
@@ -457,7 +457,8 @@ function auth_sync_users ($bulk_insert_records = 1000, $do_updates=1) {
                 $value = ldap_get_values_len($ldapconnection, $entry,$CFG->ldap_user_attribute);
                 $value = $value[0];
                 $count++;
-                array_push($fresult, $value);
+                // usernames are __always__ lowercase
+                array_push($fresult, moodle_strtolower($value));
                 if(count($fresult) >= $bulk_insert_records){
                     auth_ldap_bulk_insert($fresult);
                     //print var_dump($fresult);