Websphere v8.5.5 + JAX-WS generate nil tag

I have an application with EJB 3.1, Hibernate 3.3.1-GA and serveral webservices in JAX-WS running in WAS v8.5.

After upgrade Hiberante to 4.2.18, all webservices have stopped working. The XML generate from my server have new tag, and i don't know why. Like this,

<nil>false</nil>
<value xsi:type="xs:dateTime" xmlns:xs="http://ift.tt/tphNwY" xmlns:xsi="http://ift.tt/ra1lAU">2015-06-08T00:00:00.116+02:00</value>

Request before upgrade

<soapenv:Envelope xmlns:soapenv="http://ift.tt/sVJIaE">
<soapenv:Body>
    <ns2:CancelOT xmlns:ns2="http://tempuri.org/">
        <woCancel>
            <cancelRequestDateTime>2015-06-08T00:00:00.116+02:00</cancelRequestDateTime>
            <cancellationMotive>Eliminaci&#243;n de orden</cancellationMotive>
            <operationalSiteID>0713</operationalSiteID>
            <otClassID>1</otClassID>
            <otGotID>1746039</otGotID>
            <otOriginID>O7760325</otOriginID>
        </woCancel>
    </ns2:CancelOT>
</soapenv:Body>

Request after upgrade

<soapenv:Envelope xmlns:soapenv="http://ift.tt/sVJIaE">
<soapenv:Body>
    <ns2:CancelOT xmlns:ns2="http://tempuri.org/">
        <woCancel>
            <cancelRequestDateTime>
                <nil>false</nil>
                <value xsi:type="xs:dateTime" xmlns:xs="http://ift.tt/tphNwY" xmlns:xsi="http://ift.tt/ra1lAU">2015-06-08T00:00:00.116+02:00</value>
            </cancelRequestDateTime>
            <cancellationMotive>Eliminaci&#243;n de orden</cancellationMotive>
            <operationalSiteID>0713</operationalSiteID>
            <otClassID>
                <nil>false</nil>
                <value xsi:type="xs:int" xmlns:xs="http://ift.tt/tphNwY" xmlns:xsi="http://ift.tt/ra1lAU">1</value>
            </otClassID>
            <otGotID>1746039</otGotID>
            <otOriginID>O7760325</otOriginID>
        </woCancel>
    </ns2:CancelOT>
</soapenv:Body>

Anyone have a idea?