incorrect jsr181 mtom response

I have a method:
DataSource getDocumentContents(String documentId, String User)
This method correctly returns data when using an xfire binding with mtom enabled.
---------------------------------------------------------------------------------------------------------------------------
HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
X-Powered-By: Servlet 2.4; JBoss-4.0.4.GA (build: CVSTag=JBoss_4_0_4_GA date=200605151000)/Tomcat-5.5
Content-Type: multipart/related; type="application/xop+xml"; start="<soap.xml@xfire.codehaus.org>"; start-info="text/xml"; boundary="----=_Part_0_9582018.1172678387638"
Transfer-Encoding: chunked
Date: Wed, 28 Feb 2007 15:59:47 GMT

2de

------=_Part_0_9582018.1172678387638
Content-Type: application/xop+xml; charset=UTF-8; type="text/xml"
Content-Transfer-Encoding: 8bit
Content-ID: <soap.xml@xfire.codehaus.org>

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><soap:Body><GetDocumentContentsResponse xmlns="http://services.genome.sterling.com/documentmanagementservice/1.0"><out xmlns:ns1="http://www.w3.org/2004/11/xmlmime" ns1:mimeType="text/xsl"><Include xmlns="http://www.w3.org/2004/08/xop/include" href="cid:11726783876221-1132704612@http://www.w3.org/2001/XMLSchema" /></out></GetDocumentContentsResponse></soap:Body></soap:Envelope>
155f

------=_Part_0_9582018.1172678387638
Content-Type: text/xsl; charset=Cp1252
Content-Transfer-Encoding: binary
Content-ID: <11726783876221-1132704612@http://www.w3.org/2001/XMLSchema

<xsl:stylesheet version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
...
-----------------------------------------------------------------------------------------------------------------------------------------------

It returns an empty datasource when using mtom on a jsr181.
------------------------------------------------------------------------------------------------------------------------------------------------
HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
X-Powered-By: Servlet 2.4; JBoss-4.0.4.GA (build: CVSTag=JBoss_4_0_4_GA date=200605151000)/Tomcat-5.5
Content-Type: multipart/related; type="text/xml"; start="<soap-request>"; boundary="----=_Part_1_24702933.1172677822614"
Transfer-Encoding: chunked
Date: Wed, 28 Feb 2007 15:50:22 GMT

277
------=_Part_1_24702933.1172677822614
Content-Type: text/xml; charset=us-ascii
Content-Transfer-Encoding: 7bit
Content-ID: <soap-request>

<?xml version='1.0' encoding='UTF-8'?><soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"><soap:Body><GetDocumentContentsResponse xmlns="http://services.genome.sterling.com/documentmanagementservice/1.0"><out xmlns:ns1="http://www.w3.org/2004/11/xmlmime" ns1:mimeType="text/xsl"><Include xmlns="http://www.w3.org/2004/08/xop/include" href="cid:117267782259871164778262@http://www.w3.org/2001/XMLSchema" /></out></GetDocumentContentsResponse></soap:Body></soap:Envelope>
bf

------=_Part_1_24702933.1172677822614
Content-Type: text/xsl; charset=us-ascii
Content-Transfer-Encoding: 7bit
Content-ID: <117267782259871164778262@http://www.w3.org/2001/XMLSchema>

2b

-----=_Part_1_24702933.1172677822614-

0
---------------------------------------------------------------------------------------------------------------------------------------------------------

If I change the return type to a String then the contents are returned.