diff --git a/lib/account_component/account.rb b/lib/account_component/account.rb
index 6ee642f..3b55a94 100644
--- a/lib/account_component/account.rb
+++ b/lib/account_component/account.rb
@@ -4,7 +4,7 @@ class Account
 
     attribute :id, String
     attribute :customer_id, String
-    attribute :balance, Numeric, default: 0
+    attribute :balance, Numeric, default: -> { 0 }
     attribute :opened_time, Time
     attribute :closed_time, Time
     attribute :sequence, Integer