OpenJPA and auto-commit

Hi OpenJPA Guru's,

I'm encountering an issue when openJPA participates to a global
transaction, I've got this weird error happening sometimes:

Caused by: <openjpa-2.3.0-r422266:1540826 nonfatal general error>
org.apache.openjpa.persistence.PersistenceException:
setAutoCommit(true) invalid during global transaction.

at org.apache.openjpa.jdbc.meta.MappingTool.record(MappingTool.java:559)

at org.apache.openjpa.jdbc.meta.MappingTool.record(MappingTool.java:455)

My persistence.xml is as simple as it can be:
[code]

<persistence-unit name="${project.artifactId}Pu" transaction-type="JTA">

<provider>org.apache.openjpa.persistence.PersistenceProviderImpl</provider>

<jta-data-source>osgi:service/javax.sql.DataSource/(&(
osgi.jndi.service.name
=${project.parent.artifactId}.database)(aries.managed=true))</
jta-data-source>

<properties>

<property name="openjpa.Log" value="slf4j"/>

<property name="openjpa.jdbc.SynchronizeMappings" value=
"buildSchema(ForeignKeys=true,SchemaAction=refresh)"/>

<property name="openjpa.jdbc.DBDictionary" value="derby"/>

</persistence-unit>
[/code]

Is there any property/option to set somewhere?

Regards,

Full OSGI/EE stack made with Karaf:
https://github.com/OsgiliathEnterprise/net.osgiliath.parent