diff --git a/stoptime.rb b/stoptime.rb
index 9ee1300..110b357 100644
--- a/stoptime.rb
+++ b/stoptime.rb
@@ -670,7 +670,7 @@ module StopTime::Controllers
   #
   # path:: /customers/_customer_id_/invoices/_invoice_number_
   # view:: Views#invoice
-  class CustomersNInvoicesX
+  class CustomersNInvoicesX < R '/customers/(\d+)/invoices/([^/]+)'
     include ActionView::Helpers::NumberHelper
     include I18n