Inconsistent variable pass from express to jade

I'm playing with Node.js, Express, Jade and MongoDB. I met a weird problem about rendering. I passed the variable "users" which is returned from db query like below and I'm pretty sure it's correct:

userProvider.findByIds(ids, function(error, users) {
  res.render('index', { users: users }); // This users here has all documents founded by Ids.
});

And in the Jade template file index.jade there is a loop:

- each user in users //-This users here has only one document after I added a new user

It does not work after I added a new user every time. It only shows one user which is the latest added user. But if I restart Node.js, it works correct and shows every user included the latest one.

I guess there is some cache issue with such things. Any idea about this?