Form vs. XML: Nillable

When I go from XML to Form, the Form view automatically changes certain XML elements to nil="true". This causes an error during a SOAP tranmission.

For Example (XML view):

<Identifier xmlns="http://xchange.com/service/data/2009/3">
<Value>Blah</Value>
<SchemeOwner>Provider</SchemeOwner>
<Scheme/>
</Identifier>

I go to Form view, and when I return to XML view I get:

<Identifier xmlns="http://xchange.com/service/data/2009/3">
<Value>Blah</Value>
<SchemeOwner>Provider</SchemeOwner>
<Scheme xsi:nil="true"/>
</Identifier>

Are there any settings I can select to leave the blank values blank? Its the last piece from soapui being the perfect solution.

Thanks,
Greg