diff --git a/apps/settings/lib/Controller/UsersController.php b/apps/settings/lib/Controller/UsersController.php
index f7e5c35cb1a..4dfc6e0d71e 100644
--- a/apps/settings/lib/Controller/UsersController.php
+++ b/apps/settings/lib/Controller/UsersController.php
@@ -361,7 +361,7 @@ class UsersController extends Controller {
 									$twitter,
 									$twitterScope
 	) {
-		$email = strtolower($email);
+		$email = !is_null($email) ? strtolower($email) : $email;
 		if (!empty($email) && !$this->mailer->validateMailAddress($email)) {
 			return new DataResponse(
 				[