How can I force Hibernate to use the JDBC3 getGeneratedKeys() function?

I'm using Informix 9.4, and I get always the following message in the logfile :
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09:01:10,403 INFO SettingsFactory:105 - Use JDBC3 getGeneratedKeys(): false
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I'm using the following hibernate.cfg.xml :

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<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN" "http://hibernate.sourceforge.net/hibernate-configuration-2.0.dtd">

<hibernate-configuration>
<session-factory>
<property name="connection.datasource">java:comp/env/jdbc/Timesheet</property>
<property name="show_sql">false</property>
<!-- <property name="dialect">net.sf.hibernate.dialect.MySQLDialect</property> -->
<property name="dialect">net.sf.hibernate.dialect.Informix9Dialect</property>
<property name="jdbc.use_getGeneratedKeys">true</property>
<!-- Mapping files -->
<mapping resource="User.hbm.xml"/>
<mapping resource="Client.hbm.xml"/>
<mapping resource="Activityclient.hbm.xml"/>
<mapping resource="Activityprocedure.hbm.xml"/>
<mapping resource="Projectclient.hbm.xml"/>
<mapping resource="Activityentry.hbm.xml"/>
<mapping resource="Department.hbm.xml"/>
<mapping resource="Division.hbm.xml"/>
<mapping resource="Process.hbm.xml"/>
<mapping resource="Project.hbm.xml"/>
<mapping resource="Timeentry.hbm.xml"/>
<mapping resource="Language.hbm.xml"/>
</session-factory>
</hibernate-configuration>
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Thanx

hibernate.jdbc.use_get_generated_keys

N.b.: javadoc is inverted in the source