diff --git a/global/overlay/etc/puppet/modules/soc/manifests/sso.pp b/global/overlay/etc/puppet/modules/soc/manifests/sso.pp
index 7917c8c..0ab6340 100644
--- a/global/overlay/etc/puppet/modules/soc/manifests/sso.pp
+++ b/global/overlay/etc/puppet/modules/soc/manifests/sso.pp
@@ -39,7 +39,7 @@ class soc::sso(
   Array             $passthrough        = [],
   Boolean           $x_remote_user      = false,
   Boolean           $remote_user        = false,
-  String            $user_header        = undef,
+  Optional[String]  $user_header        = undef,
   Boolean           $unset_auth_header  = false,
   Boolean           $single_user        = false,
   Boolean           $satosa             = true,