diff --git a/certbot.cf b/certbot.cf
index c811c1e..64c0b18 100644
--- a/certbot.cf
+++ b/certbot.cf
@@ -42,10 +42,13 @@ packages:
 			handle => "certbot_installed";
 }
 
-bundle agent certbot_cert(site,webroot,domain)
+bundle agent certbot_cert(site,webroot)
 {
 
 vars:
+
+	"domain" string => "$(site[domain])";
+
 	"site_json" string => storejson(@(site));
 	"args" string => string_mustache(
 			"-d {{domain}} {{#aliases}} -d {{.}} {{/aliases}}",
@@ -71,7 +74,8 @@ classes:
 	or => {no_cert_file, certbot_repaired};
 
 defaults:
-	 "webroot" string => "standalone";
+	"webroot" string => "standalone";
+	"domain" string => "$(site[domain])";
 
 methods:
 	"any" usebundle => install_certbot;