soap wrong xml serialization

I have a wsld definition that looks like

...
<sequence>
    <element name="version" nillable="false" type="xsd:string"/>
    <element name="payment" nillable="false" type="tns1:payment"/>
   ...
</sequence>
...

This is the xml log of the request that is sent

<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:ns0="http://ift.tt/1oN8dni" ...>
<SOAP-ENV:Header/>
<ns2:Body>
<ns0:doWebPaymentRequest>
<ns0:version>
    <ns0:version>4</ns0:version>
    <ns0:payment>
        <ns1:amount>33300</ns1:amount>
        ...
    </ns0:payment>
</ns0:version>
...

So suds encloses a payment object into version (a string), and it breaks the request. Why is that ?? Any way to go around this ?