empty parameter without character =

I am missing the ability to build a REST query string like "http://sample:8080/path/down?wsdl". The only parameter required is wsdl. There is no value assigned and it must not have a character = at the end of the query.
I was successful building a query like "http://sample:8080/path/down?wsdl=" using the option "parameter required".
As you might guess I want to fetch a wsdl definition from a SOAP based web service and test the content.