Dozer - how to map base classes only

Question

I have ClassA, ClassB, ClassC where:

ClassB extends ClassA
ClassC extends ClassA

I wanted to map only ClassA in my dozer configuration and wrote this:

<mapping wildcard="false">
        <class-a>ClassA</class-a>
        <class-b>ClassA</class-b>
        <field custom-converter="MyConverter">
            <a>value</a>
            <b>value</b>
        </field>
    </mapping>

However, when I do mapper.map(instB, instB) the custom converter from ClassA never gets called.

Thank you!