Vista - Add Processing Instructions to SOAP response messages

This is probably simple (I'm very new to WCF!) but I've been searching
for hours with no luck. I am replacing an ASP.NET web service with a
WCF service. I'm using basichttpbinding because the service is getting
called from a java app. They seem to be having trouble processing the
result message and they believe it's because there is no XML
declaration (processing instruction).

The original response (they could process fine)...

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<soap:Body>
<ReceiveTransactionResponse xmlns="http://tempuri.org/">
<ReceiveTransactionResult>true</ReceiveTransactionResult>
</ReceiveTransactionResponse>
</soap:Body>
</soap:Envelope>

The new response from the WCF service...
<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
<s:Header>
<ActivityId
CorrelationId="f0f7836d-d14c-47bd-bb40-ff1c049a2ac2"
xmlns="http://schemas.microsoft.com/2004/09/ServiceModel/Diagnostics">601dfdd7-8cf1-4cff-a13b-3f0243415178</ActivityId>
</s:Header>
<s:Body>
<ReceiveTransactionResponse xmlns="http://tempuri.org/">
<ReceiveTransactionResult>true</ReceiveTransactionResult>
</ReceiveTransactionResponse>
</s:Body>
</s:Envelope>

Is there a property or attribute I can use so the xml declaration will
be included in the response message? I found that I can use message
contracts to change the body, header, etc but there doesn't seem to be
any way to use a message contract to specify that the xml declaration
should be included.

Thanks,
Greg