diff --git a/manifests/varnish/vhost.pp b/manifests/varnish/vhost.pp
index 27ddc3a..6b9baef 100644
--- a/manifests/varnish/vhost.pp
+++ b/manifests/varnish/vhost.pp
@@ -1,15 +1,15 @@
 # Virtual host definition for varnish
 
 define profile::varnish::vhost (
   String $servername = $title,
   String $order = '50',
   Array[String] $aliases = [],
   Optional[String] $vcl_recv_extra = undef,
   Optional[String] $vcl_deliver_extra = undef,
-  Optional[String] $hsts_max_age = undef,
+  Variant[Undef, String, Integer[1]] $hsts_max_age = undef,
 ) {
   ::profile::varnish::vcl_include {"vhost_${servername}":
     order   => $order,
     content => template('profile/varnish/vhost.vcl.erb'),
   }
 }