Issue with isXML/isJson on ConnectManager

The method isXML on ConnectManager doesn't works properly

I'm having issues with a request to the following url:

http://services.tvrage.com/feeds/search.php?show=orange%20black

On this method it is checking two fixed content types:

"application/xml","application/xml;charset=utf-8"

but the response of this url is returning: "text/xml; charset=UTF-8"
which doesn't match with any of them.