Savon SOAP: How to avoid 'soap:' prefix on request body tags?

Savon is currently producing tags like this: <soap:orderid>R211758537</soap:orderid>

How do I get tags like this, without the soap prefix? <orderid>R211758537</orderid>

Here's the code I am using:

endpoint = "http://www.ioperate.net/ws/order/orderws.asmx?wsdl"
response = session.开发者_Python百科request endpoint, 'OrderUpload' do
  http.headers["SOAPAction"] = "http://chrome52/webservices/OrderUpload" 

  soap.body = {
    :orderid => R211758537
  }
end