Is there a way to override the DefaultSchema of a fluent nhibernate configuration in the map class?

Question

Background

I am working on a .net standard 2.0 library that is using FluentNhibernate 2.1.2. Its fluent nhibernate configuration is set to use a default schema.

Fluently.Configure().Database(() => {
    var db = PostgreSQLConfiguration.PostgreSQL82;
    ...
    ...
    ...
    ...
    db.DefaultSchema('app');
});

Problem

I am trying to add a class map that is under a different schema in the database than the default one.
Using Schema('example') in the class map's constructor just concatenates the schema to the default one.
Is there a way to override the schema for a specific mapping?