PN Problem with Non-Functional Currency

 When trying to create payment schedule /Billing in non Functional currency ,System does not allow to to create Payment schedule . It gives error massage Corporate Rate is not defined.

Steps to reproduce:

Setup > System option > Currency Conversion Type#Corporate . Create Lease in USD functional currency and Payment Term in MXN . When trying to Query payment term system throw error massage# APP-PN_49080 : The conversion Rate for this currency code is not defined .  Please select another Currents , or contact our system Administrator.

I think System should allow to Create Transaction but this error should come when trying to approve this transaction . But in case of Rate Type #user system is allowing to create Transaction but it is taking Corporate conversion Rate when Payment going in AP /AR.