diff --git a/nginx/nginx.conf b/nginx/nginx.conf
index 1674152b..6b0a47ed 100644
--- a/nginx/nginx.conf
+++ b/nginx/nginx.conf
@@ -86,6 +86,7 @@ http {
 
         root /var/empty;
 
+        # use $host to set up HSTS for redirect domains
         return 301 https://$host$request_uri;
     }