diff --git a/manifests/init.pp b/manifests/init.pp
index 29623b5..0f57742 100644
--- a/manifests/init.pp
+++ b/manifests/init.pp
@@ -344,7 +344,7 @@ class mastodon (
     request_headers          => [
       'set X-Forwarded-Proto "https"',
     ],
-    headers                  => 'always set Strict-Transport-Security "max-age=31536000"',
+    headers                  => ['always set Strict-Transport-Security "max-age=31536000"'],
     directories              => [
       {
         'path'     => '^/(assets|avatars|emoji|headers|packs|sounds|system)',