diff --git a/controllers/matrix_chat.php b/controllers/matrix_chat.php
index 4fa86ce47504f052a1f1e29b3b5dbe58e283530d..f80088b592e658d19e918d0d8399480acd8f6eb5 100644
--- a/controllers/matrix_chat.php
+++ b/controllers/matrix_chat.php
@@ -61,7 +61,7 @@ class MatrixChatController extends AuthenticatedController
             if (!$this->account && !Config::get()->MATRIX_AUTO_CREATE_ACCOUNTS) {
                 $this->account = new MatrixAccount();
                 $this->account->user_id = User::findCurrent()->id;
-                $this->account->matrix_account_id = '@' . User::findCurrent()->username . ':' .
+                $this->account->matrix_account_id = '@' . strtolower(User::findCurrent()->username) . ':' .
                     Config::get()->MATRIX_ACCOUNTS_LOCAL_PART;
                 $this->account->matrix_password = '';
                 $this->account->store();