diff --git a/config/routes.rb b/config/routes.rb
index c5dd020..4f0ce00 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -29,7 +29,7 @@ Rails.application.routes.draw do
     resources :versions, only: [:show]
   end
 
-  constraints subdomain: 'api' do
+  constraints subdomain: /^api(\.|$)/ do
     namespace :api, path: nil do
       namespace :v1 do
         resources :cards, only: [:index, :show]