Cannot convert value of type 'UInt' to expected argument type 'UnsafeMutablePointer<UInt>'

I am trying to initialize a String from the content accessible by a URL:

actualresponse.response = String(contentsOfURL: url, usedEncoding: NSUTF8StringEncoding)

I get the following error thrown, pointing at the usedEncoding:

Cannot convert value of type 'UInt' to expected argument type 'UnsafeMutablePointer'

Can anyone tell me why this error is thrown and how I can fix it?