Parent's Validations lost via Inheritance

I have some simple models that inherit from a parent (using STI). In
all but one case, all of the validations are declared in the parent
model like:

  class InfoRequest < ActiveRecord::Base
    validates_presence_of :full_name,
                          :email_address,
                          :phone_number,
                          :mailing_address
    ... etc ...
  end

In one of the child models, I need to add one more validation rule (it
has an extra attribute) like so:

  class CreditInfoRequest < InfoRequest
    validates_acceptance_of :auth_to_share
  end

Except doing this seems to blow away all my validations for this model.
If I don't declare any validations in the child model, the parent's
validations are inherited and run just fine. But the minute I add
validations to the child, both it's *and* the inherited validations fail
to run.

What?

BTW, I can get around this by overriding the validate method in the
child model but that just bugs me.

Can someone shed some light on this?

-Chris