Fedex Plugin Rails

Question

I working on an existing code base for a client. The app is built in rails 2.3 and uses the fedex plugin. Now i have develop a functionality for shipping the goods using international priority service type, the problem i'm facing is when ever i make a call to the fedex api for a shipping label it returns an error

 "Fedex::FedexError: Unable to get label from Fedex: Customs Value is required"

Can some one help me how to mention the customs value for the label.

This is how my code is:

price, labels, tracking_number = fedex.label(

        :shipper => { :contact => shipper, :address => origin },
    :recipient => { :contact => recipient, :address => destination.merge(:residential => false) },
    :service_type => service_type,       
        :packages => [{:length => 3,
                       :height => 4,
                       :width => 5,
                       :weight => 5,
                      }],
    :weight => 5,
    :commodities => commodities,
    :customs_value =>{:currency => "USD", :amount => "100" },
    :residential => is_residential_destination
)

Thanks in advance.