diff --git a/app/mailers/spree/order_mailer.rb b/app/mailers/spree/order_mailer.rb
index 4cd6676c59d..ce9b79874e7 100644
--- a/app/mailers/spree/order_mailer.rb
+++ b/app/mailers/spree/order_mailer.rb
@@ -3,7 +3,7 @@
 module Spree
   class OrderMailer < BaseMailer
     helper HtmlHelper
-    helper CheckoutHelper
+    helper ::CheckoutHelper
     helper SpreeCurrencyHelper
     helper OrderHelper
     include I18nHelper