Is StringFormatMethod working?

Hi, its my understand of the StringFormatMethodAttribute that it should get Resharper to perform the same analysis as string.format().

I have an extension method that looks like this:

        [StringFormatMethod("s")]
        public static string F(this string s, params object[] args)
        {
            return string.Format(s, args);
        }

However Resharper is not analysing this method and applying the squiggly underlines. Am I misunderstanding something or does something else need to be configured?