diff --git a/install/tpl/apache_ispconfig.vhost.master b/install/tpl/apache_ispconfig.vhost.master
index 8eccbcba3894542819ac94b2ae255e16b2c5fc5f..5c4ef22485471b4c490e8a52e3b71e473122a127 100644
--- a/install/tpl/apache_ispconfig.vhost.master
+++ b/install/tpl/apache_ispconfig.vhost.master
@@ -88,7 +88,7 @@ NameVirtualHost *:<tmpl_var name="vhost_port">
   </tmpl_if>
 
   <IfModule mod_headers.c>
-    Header always add Strict-Transport-Security "max-age=15768000"
+    Header setifempty Strict-Transport-Security "max-age=15768000"
 	RequestHeader unset Proxy early
   </IfModule>