ClassWithNullColumns.hbm.xml

<?xml version="1.0" encoding="utf-8" ?> 
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" default-lazy="false">

<class 
		name="NHibernate.DomainModel.NHSpecific.ClassWithNullColumns, NHibernate.DomainModel" 
		table="usertype">

		<id name="Id" column="id">
			<generator class="assigned" />
		</id>

		<property 
			name="FirstInt32" 
			type="NHibernate.DomainModel.NHSpecific.NullInt32UserType, NHibernate.DomainModel" 
			column="f_int32"
			not-null="false"
		/>

		<property 
			name="SecondInt32" 
			type="NHibernate.DomainModel.NHSpecific.NullInt32UserType, NHibernate.DomainModel" 
			column="s_int32"
			not-null="false"
		/>

	</class>
</hibernate-mapping>