Is there a way to append something to the query string with no value set?

I would like to see this kind of URL being generated: http://local/things?magic.

What I'm looking for is when the user goes to http://local/other?magic then every URL in the generated page would contain magic in the end.

Following code is almost a solution but it gives me http://local/things?magic=. There is an extra = that I don't want there.

def default_url_options(options)
    if params.has_key?("magic")
        { :magic => "" }
    end
end

Setting { :magic => nil } will remove the magic entirely from the generated URLs.