LP_CUSTOMER_RANK and Initial Customer Account Creation

It appears to be the case on our system that if a simple constituent account is created in the client, i.e. you add all your information directly into the General Tab and don't go elsewhere before saving, then LP_CUSTOMER_RANK is called on that save, but no customer number is supplied, so it can't do anything.  This is turning out to be a problem for us, as we are using that procedure to apply organization-specific constituencies in our consortium.  Has anyone else observed this behavior?