Thanks for that quick reply:

I simplified my code to a working example that produces same error.

Log: INFO: HHH000412: Hibernate Core {4.1.4.Final}

Mapping:

<hibernate-mapping>
<class name="package.Node" table="node" catalog="database">
<id name="id" type="java.lang.Integer">
<column name="id" />
<generator class="identity" />
</id>
<natural-id mutable="true">
<property name="name" type="string">
<column name="name" length="64" not-null="true" />
</property>
<many-to-one name="parent" class="package.Node" lazy="false" fetch="select" update="false">
<column name="parent" />
</many-to-one>
</natural-id>
</class>
</hibernate-mapping>

// check for existence
final NaturalIdLoadAccess nila = session.byNaturalId(Node.class);
nila.using("name", "test");
nila.using("parent", null);
Node node = (Node) nila.load(); // fires exception

if (node == null)
{
node = new Node();
node.setName("test");

session.save(pc);
}