diff --git a/interface/web/dns/form/dns_soa.tform.php b/interface/web/dns/form/dns_soa.tform.php
index 66c26655dbc03ffe1b4930b7b957b938c2205306..66ac1031dd3e38cdb4b53d557ad0b1714817493c 100644
--- a/interface/web/dns/form/dns_soa.tform.php
+++ b/interface/web/dns/form/dns_soa.tform.php
@@ -108,7 +108,7 @@ $form["tabs"]['dns_soa'] = array (
 			'validators'	=> array ( 	0 => array (	'type'	=> 'NOTEMPTY',
 														'errmsg'=> 'mbox_error_empty'),
 										1 => array (	'type'	=> 'REGEX',
-														'regex' => '/^[[a-zA-Z0-9\.\-]{0,64}\.$/',
+														'regex' => '/^[[a-zA-Z0-9\.\-\_]{0,64}\.$/',
 														'errmsg'=> 'mbox_error_regex'),
 									),
 			'default'	=> '',