Mixing <Joined-subclass> and <subclass>

I'm actually adding a functionality in a product (Hibernate & Spring intensive use) and I have to modify the actual Hibernate mapping, here's the deal :

the "Mother" entity (abstract) class and called AbstractElement

<class abstract="true" dynamic-insert="true" dynamic-update="true" name="fr.g.n.a.domain.instances.AbstractElement"
table="AEL_ABSTRACT_ELEMENT">
<cache usage="read-write" />
<id name="oid" type="string">
  <column length="64" name="OID" />
  <generator class="assigned" />
</id>
<discriminator column="TYPELEMENT" type="string" not-null="false" force="true" />

<!-- Version hibernate de l'objet persisté : -1 signifie que l'objet n'est pas présent en base -->
<version name="version" unsaved-value="negative">
  <column name="VERSION" />
</version>

a sub class (not abstract) which enhances the concept called "ElementNiveauUn", here's a snippet of it mapping

 <joined-subclass dynamic-insert="true" dynamic-update="true" name="fr.g.n.a.domain.instances.ElementNiveauUn"
table="ENU_ELEMENT_NIVEAU_UN" abstract="true" lazy="false" extends="fr.generali.nova.atp.domain.instances.AbstractElement">
<key column="OID" not-null="true" foreign-key="FK_ENU_AEL_OID" />

until here, every thing is running well, nothing special to mention about the java classes, here's my problem :

I have to add a class (non abstract) which extends ElementNiveauUn in order to inherit from it, and so from "AbstractElement".

The snippet of the mapping looks like this:

  <subclass name="fr.g.n.a.domain.parametrage.Critere" extends="fr.g.n.a.domain.instances.ElementNiveauUn" >
    <subclass dynamic-insert="true" dynamic-update="true" name="fr.g.n.a.parametrage.CritereProduit" abstract="false" lazy="false"
  extends="fr.g.n.a.domain.parametrage.Critere" discriminator-value="CRITERE_PRODUIT">
    </subclass>
    <subclass dynamic-insert="true" dynamic-update="true" name="fr.g.n.a.domain.parametrage.Segmentation" abstract="false" lazy="false"
  extends="fr.g.n.a.atp.domain.parametrage.Critere" discriminator-value="SEGMENTATION">
    </subclass>
    <subclass dynamic-insert="true" dynamic-update="true" name="fr.g.n.a.domain.parametrage.CritereApporteur" abstract="false" lazy="false"
  extends="fr.g.n.a.atp.domain.parametrage.Critere" discriminator-value="CRITERE_APPORTEUR">
    </subclass>

when I try to save an instance of Segmentation I have this kind of Exception (using H2 and UDBUnit)

Caused by: org.h2.jdbc.JdbcSQLException: NULL not allowed for column "ID_ELEMENT_NIVEAU_UN"; SQL statement: insert into ENU_E开发者_开发问答LEMENT_NIVEAU_UN (OID) values (?) [23502-154]

and the generated SQL for the insertion of Segmentation looks like this

insert into ENU_ELEMENT_NIVEAU_UN (OID) values (?)

It seems that it considered Segmentation as an ElementNiveauUn but because of ENU_ELEMENT_NIVEAU_UN is not-null="true" within the ElementNiveauUn mapping it's expecting to set the value which I already did but it's seems lost during the insertion process

Here's a simplified UML class diagram : http://goo.gl/vOHHC