diff --git a/guides/source/developers/promotions/promotion-rules.html.md b/guides/source/developers/promotions/promotion-rules.html.md
index 7d998cff06f..6c3221a955b 100644
--- a/guides/source/developers/promotions/promotion-rules.html.md
+++ b/guides/source/developers/promotions/promotion-rules.html.md
@@ -100,6 +100,7 @@ You must then register the custom rule in an initializer in your
 `config/initializers/` directory:
 
 ```ruby
+# config/initializers/spree.rb
 Rails.application.config.spree.promotions.rules << Spree::Promotion::Rules::MyPromotionRule
 ```