diff --git a/README.md b/README.md
index c330642..25a3e92 100644
--- a/README.md
+++ b/README.md
@@ -363,7 +363,10 @@ You'll need apache2-utils on the machine where you plan to create the htpasswd f
 
 ### vouch-proxy Authentication Support
 
-You can also secure your virtual hosts by using the auth_request nginx module in conjunction with the authentication proxy [vouch-proxy](https://github.com/vouch/vouch-proxy)
+You can also secure your virtual hosts by using the auth_request nginx module in conjunction with the authentication proxy [vouch-proxy](https://github.com/vouch/vouch-proxy).
+Set the following variables on the container you want secured:
+VOUCH_INTERNAL_LOCATION - private URL to your vouch-proxy instance, to perform validations again
+VOUCH_EXTERNAL_LOCATION - public URL to your vouch-proxy instance
 
 ```yaml
   authtest: