diff --git a/lib/private/User/Manager.php b/lib/private/User/Manager.php
index 4a42a397a8e..7ac42425c0e 100644
--- a/lib/private/User/Manager.php
+++ b/lib/private/User/Manager.php
@@ -694,8 +694,8 @@ class Manager extends PublicEmitter implements IUserManager {
 		$l = Server::get(IFactory::class)->get('lib');
 
 		// Check the ID for bad characters
-		// Allowed are: "a-z", "A-Z", "0-9", spaces and "_.@-'"
-		if (preg_match('/[^a-zA-Z0-9 _.@\-\']/', $uid)) {
+		// Allowed are: "a-z", "A-Z", "0-9", spaces and "_.@-'#"
+		if (preg_match(‘/[^a-zA-Z0-9 _.@\-'#]/’, $uid)) {
 			throw new \InvalidArgumentException($l->t('Only the following characters are allowed in an Login:'
 				. ' "a-z", "A-Z", "0-9", spaces and "_.@-\'"'));
 		}