Behavior of NodeJS require

I'm trying out sample code on http://sequelizejs.com/ main page. Under "simple usage" the first two lines of code are as follows:

var Sequelize = require('sequelize')
  , sequelize = new Sequelize('database', 'username', 'password')

I noticed that when I changed the code to the following, everything stops working.

var Sequelize = require('sequelize')
  , sequelize = new require('sequelize')('database', 'username', 'password')

From my understanding, the 2 lines above should do the exact same thing. Why is my understanding wrong?