diff --git a/static/js/pages/setup.js b/static/js/pages/setup.js
index 90e32a403..bb7c50092 100644
--- a/static/js/pages/setup.js
+++ b/static/js/pages/setup.js
@@ -16,7 +16,7 @@
       return;
     }
 
-    $scope.HOSTNAME_REGEX = '^[a-zA-Z-0-9\.]+(:[0-9]+)?$';
+    $scope.HOSTNAME_REGEX = '^[a-zA-Z-0-9_\.\-]+(:[0-9]+)?$';
 
     $scope.validateHostname = function(hostname) {
       if (hostname.indexOf('127.0.0.1') == 0 || hostname.indexOf('localhost') == 0) {