How do I get the count of rows using Bookshelf?

How can I get the number of rows (without any filter)?

I've tried this User.fetch().count() and User.count(), but I get these errors respectively:

TypeError: User.fetch is not a function

AssertionError: expected { Object (_bitField, _fulfillmentHandler0, ...) } to equal 0

Here's my model:

let bookshelf = require('../config/database');

require('./role');

var User = bookshelf.Model.extend({
    tableName: 'users',
    role: function() {
        return this.hasOne(Role);
    }
});

module.exports = bookshelf.model('User', User);

via Juliano Nunes Silva Oliveira