diff --git a/config.ru b/config.ru
index c1d0e930a589d34a0806c0caa3af3dd33d7947a1..209997d02a990a8e958108fb139b4a463b74f1f8 100644
--- a/config.ru
+++ b/config.ru
@@ -154,7 +154,7 @@ class CreditCardCustomerGateway
 	end
 
 	def customer_plan
-		name = DB.exec_params(<<~SQL, [customer_id]).first&.[]("plan_name")
+		name = DB.exec_params(<<~SQL, [@customer_id]).first&.[]("plan_name")
 			SELECT plan_name FROM customer_plans WHERE customer_id=$1 LIMIT 1
 		SQL
 		PLANS.find { |plan| plan[:name].to_s == name }