diff --git a/classes/loginflow/authcode.php b/classes/loginflow/authcode.php
index 82fcd54..1885865 100644
--- a/classes/loginflow/authcode.php
+++ b/classes/loginflow/authcode.php
@@ -607,8 +607,8 @@ protected function handlelogin(string $oidcuniqid, array $authparams, array $tok
                 // Handle username change - update token, update connection.
                 if ($usernamechanged) {
                     $potentialduplicateuser = core_user::get_user_by_username($oidcusername);
-                    if ($potentialduplicateuser) {
-                        // Username already exists, cannot change Moodle account username, throw exception.
+                    if ($potentialduplicateuser->id!=$tokenrec->userid) {
+                        // Username already exists in another user, cannot change Moodle account username, throw exception.
                         throw new moodle_exception('erroruserwithusernamealreadyexists', 'auth_oidc', null, null, '2');
                     } else {
                         // Username does not exist:
diff --git a/lib.php b/lib.php
index 17cf0d1..c8f6734 100644
--- a/lib.php
+++ b/lib.php
@@ -177,7 +177,7 @@ function auth_oidc_get_tokens_with_mismatched_usernames() {
               FROM {auth_oidc_token} tok
               JOIN {user} u ON u.id = tok.userid
              WHERE tok.userid != 0
-               AND u.username != tok.username';
+               AND u.username COLLATE utf8mb4_general_ci != tok.username COLLATE utf8mb4_general_ci';
     $records = $DB->get_recordset_sql($sql);
     foreach ($records as $record) {
         $item = new stdClass();