diff --git a/auth/ldap/lib.php b/auth/ldap/lib.php
index 1ba88dc..598d390 100644
--- a/auth/ldap/lib.php
+++ b/auth/ldap/lib.php
@@ -452,7 +452,8 @@ 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);