visionmedia/express — pull request #1589 by hacksparrow (2013-04-23 17:32:28+00:00)
Title: Signed cookies can now accept numbers as values, like unsigned cookies

Fixed this issue:

var count = 1;
res.cookie('count', count); // works
res.cookie('count', count, { signed: true }); // throws

Details: https://github.com/visionmedia/express/issues/1588