diff --git a/interface/lib/classes/custom_datasource.inc.php b/interface/lib/classes/custom_datasource.inc.php
index 17aa7a295219b514aa5de01cd9823d94834bc7f6..35bf7d55dc29f63b30cb6cf0f0b3bf40cd1607a1 100644
--- a/interface/lib/classes/custom_datasource.inc.php
+++ b/interface/lib/classes/custom_datasource.inc.php
@@ -105,6 +105,9 @@ class custom_datasource {
 			case 'default_dnsserver':
 				$field = 'dns_server';
 			break;
+			case 'default_slave_dnsserver':
+				$field = 'dns_server';
+			break;
 			case 'default_fileserver':
 				$field = 'file_server';
 			break;