Add check for defined

manifests/init.pp

@@ -360,9 +360,11 @@ class mastodon (
     timeout     => 0,
     require     => File["${mastodon_home}/live/.env.production"],
   }
-  class { 'letsencrypt':
-    email             => $cert_admin_mail,
-    renew_cron_ensure => 'present',
+  if (!defined(Class['letsencrypt'])) {
+    class { 'letsencrypt':
+      email             => $cert_admin_mail,
+      renew_cron_ensure => 'present',
+    }
   }
   letsencrypt::certonly { $hostname:
     domains            => [$hostname],