Mongoose findByIdAndUpdate not returning correct model

I have an issue I've not seen before with the Mongoose findByIdAndUpdate not returning the correct model in the callback.

Here's the code:

    var id = args._id;
    var updateObj = {updatedDate: Date.now()};
    _.extend(updateObj, args);

    Model.findByIdAndUpdate(id, updateObj, function(err, model) {
        if (err) {
            logger.error(modelString +':edit' + modelString +' - ' + err.message);
            self.emit('item:failure', 'Failed to edit ' + modelString);
            return;
        }
        self.emit('item:success', model);
    });

The original document in the db looks like this:

{
    _id: 1234
    descriptors: Array[2],
    name: 'Test Name 1'
}

The updateObj going in looks like this:

{
    _id: 1234
    descriptors: Array[2],
    name: 'Test Name 2'
}  

The model returned from the callback is identical to the original model, not the updatedObj. If I query the db, it has been updated correctly. It's just not being returned from the database.

This feels like a 'stupid-user' error, but I can't see it. Any ideas greatly appreciated.

In Mongoose 4.0, the default value for the new option of findByIdAndUpdate (and findOneAndUpdate) has changed to false, which means returning the old doc (see #2262 of the release notes). So you need to explicitly set the option to true to get the new version of the doc, after the update is applied:

Model.findByIdAndUpdate(id, updateObj, {new: true}, function(err, model) {...