diff --git a/apps/settings/lib/Controller/UsersController.php b/apps/settings/lib/Controller/UsersController.php
index 1aeb5f83c17..c7f54f59e4c 100644
--- a/apps/settings/lib/Controller/UsersController.php
+++ b/apps/settings/lib/Controller/UsersController.php
@@ -344,7 +344,7 @@ 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(
 				[