diff --git a/htdocs/user/class/user.class.php b/htdocs/user/class/user.class.php
index 6d4530d6077..a9dcbfe3b87 100644
--- a/htdocs/user/class/user.class.php
+++ b/htdocs/user/class/user.class.php
@@ -1393,7 +1393,7 @@ class User extends CommonObject
 
 		dol_syslog(get_class($this)."::create login=".$this->login.", user=".(is_object($user) ? $user->id : ''), LOG_DEBUG);
 
-		$badCharUnauthorizedIntoLoginName = getDolGlobalString('MAIN_LOGIN_BADCHARUNAUTHORIZED', '/[,@<>"\']/');
+		$badCharUnauthorizedIntoLoginName = getDolGlobalString('MAIN_LOGIN_BADCHARUNAUTHORIZED', ',@<>"\'');
 
 		// Check parameters
 		if (!empty($conf->global->USER_MAIL_REQUIRED) && !isValidEMail($this->email)) {
@@ -1405,7 +1405,7 @@ class User extends CommonObject
 			$langs->load("errors");
 			$this->error = $langs->trans("ErrorFieldRequired", $langs->transnoentitiesnoconv("Login"));
 			return -1;
-		} elseif (preg_match($badCharUnauthorizedIntoLoginName, $this->login)) {
+		} elseif (preg_match('/['.preg_quote($badCharUnauthorizedIntoLoginName, '/').']/', $this->login)) {
 			$langs->load("errors");
 			$this->error = $langs->trans("ErrorBadCharIntoLoginName");
 			return -1;