I have the following tables I need to map:

+-------------------------+
| Person                  |
+-------------------------+
| PersonId                |
| FullName                |
+-------------------------+

+-------------------------+
| PersonAddress           |
+-------------------------+
| PersonId                |
| AddressId               |
| IsDefault               |
+-------------------------+

+-------------------------+
| Address                 |
+-------------------------+
| AddressId               |
| State                   |
+-------------------------+

And the following classes:

public class Person 
{
public virtual int Id { get; set; }
public virtual string FullName { get; set; }
}

public class PersonAddress
{
public virtual Person Person { get; set; }
public virtual Address Address { get; set; }
public virtual bool IsDefault { get; set; }
}

public class Address
{
public virtual int Id { get; set; }
public virtual string State { get; set; }
}

And finally the mappings:

public class PersonMap : ClassMap<Person>
{
public PersonMap()
{
 Id(x => x.Id, "PersonId");
}
}

public class PersonAddressMap : ClassMap<PersonAddress>
{
public PersonAddressMap()
{
 CompositeId().KeyProperty(x => x.Person, "PersonID")
              .KeyProperty(x => x.Address, "AddressID");
}
}

public class AddressMap: ClassMap<Address>
{
public AddressMap()
{
 Id(x => x.Id, "AddressId");
}
}

Assume I cannot alter the tables. If I take the mapping class (PersonAddress) out of the equation, everything works fine. If I put it back in I get:

Could not determine type for: Person, Person, Version=1.0, Culture=neutral, PublicKeyToken=null, for columns: NHibernate.Mapping.Column(PersonId)

What am I missing here? I'm sure this must be simple.