diff --git a/config/environments/production.rb.sample b/config/environments/production.rb.sample
index 4fcc4c58e49..d486132aad2 100644
--- a/config/environments/production.rb.sample
+++ b/config/environments/production.rb.sample
@@ -82,7 +82,7 @@ Discourse::Application.configure do
 
   # Discourse strongly recommend you use a CDN.
   # For origin pull cdns all you need to do is register an account and configure
-  # config.action_controller.asset_host = "http://YOUR_CDN_HERE"
+  config.action_controller.asset_host = ENV["CDN_URL"] if ENV["CDN_URL"]
 
   # a comma delimited list of emails your devs have
   # developers have god like rights and may impersonate anyone in the system