diff --git a/lib/active_merchant/billing/integrations/adyen/helper.rb b/lib/active_merchant/billing/integrations/adyen/helper.rb
index 87b296defaa..6b34b94d4ca 100644
--- a/lib/active_merchant/billing/integrations/adyen/helper.rb
+++ b/lib/active_merchant/billing/integrations/adyen/helper.rb
@@ -38,6 +38,7 @@ def initialize(order, account, options = {})
             # Do NOT call super. Super's options are too limited for Adyen
             options.assert_valid_keys([:amount, :currency, :test] + SIGNATURE_FIELDS)
             @fields = {}
+            @raw_html_fields = []
             self.order       = order
             self.account     = account
             options.each do |k, v|