Xsi:nil="true" vs type="xs:string" nillable="true" minOccurs=&quot

Hello,

I have an error with the service ‘xmlNodeToDocument’ after processing a soap message :

This message contains :

wsdl of the input document:
<xsd:element name=“fixdate” nillable=“true” type=“xsd:string” minOccurs=“0”/>

The document generated after invoking the service ‘xmlNodeToDocument’:
<record name="fixdate" javaclass="com.wm.app.b2b.services.CValues">
<value name="@xsi:nil">true</value>
</record>

the error is :
Incorrect flow Error : java.lang.Exception: INVALID List of errors: [0] pathName=/dx:troubleticket/ticket/fixdate errorCode=VV-004 errorMessage=[ISC.0082.9030] Type mismatch, String expected

Is there anybody have an explanation ?