diff --git a/config/environments/development.rb b/config/environments/development.rb
index 6f087acd595..a1360678d03 100644
--- a/config/environments/development.rb
+++ b/config/environments/development.rb
@@ -67,6 +67,7 @@ Discourse::Application.configure do
   end
 
   if hosts = ENV['DISCOURSE_DEV_HOSTS']
+    Discourse.deprecate("DISCOURSE_DEV_HOSTS is deprecated. Use RAILS_DEVELOPMENT_HOSTS instead.")
     config.hosts.concat(hosts.split(","))
   end