How to map a many-to-many linking table to use another schema?

Question

I have a few classes that I map to non-default schema using NHibernate.Mapping.Attributes like this:

[Class(Lazy = true, Schema = "NonDefaultSchemaName")]
public class Class1

I also have some many-to-many mappings:

[Set(Inverse = false, Table = "Class1ToClass2", Lazy = true, Cascade = "none")]
[Key(1, Column = "Class1ID")]
[ManyToMany(2, ClassType = typeof(Class2), Column = "Class2ID")]

What I am trying to achieve is to have the linking table Cass1ToClass2 mapped to

[NonDefaultSchemaName].[Class1ToClass2]

NHibernate automatically maps to the default schema. I could not find anything similar googling around...