diff --git a/app/controllers/split_checkout_controller.rb b/app/controllers/split_checkout_controller.rb
index aa27cfbfcb..c7396b39dd 100644
--- a/app/controllers/split_checkout_controller.rb
+++ b/app/controllers/split_checkout_controller.rb
@@ -226,7 +226,7 @@ class SplitCheckoutController < ::BaseController
 
     adjustment = voucher.create_adjustment(voucher.code, @order)
 
-    if !adjustment.valid?
+    unless adjustment.valid?
       @order.errors.add(:voucher, I18n.t('split_checkout.errors.add_voucher_error'))
       adjustment.errors.each { |error| @order.errors.import(error) }
       return false