How could router be "undefined" here in my Node app?

var express = require('express')
var router = express.Router();

I am debugging my Node app and express is defined, but after stepping over the var router line, router is still undefined, how could this happen?

Well here is all the code if you must:

var express = require('express')
//  , fancy_scripts = require('./fancy_scripts')
  , routes = require('./routes')
  , user = require('./routes/user')
  , http = require('http')
  , path = require('path');

var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');

// New Code
var mongo = require('mongodb');
var monk = require('monk');
var db = monk('localhost:27017/sparks');

var app = express();

// all environments
app.set('port', process.env.PORT || 3000);
app.set('views', __dirname + '/views');
app.set('view engine', 'jade');
app.engine('html', require('ejs').renderFile);
app.use(express.favicon());
app.use(express.logger('dev'));
app.use(express.bodyParser());
app.use(express.methodOverride());
app.use(app.router);
app.use(express.static(path.join(__dirname, 'public')));
app.use(express.static(__dirname + '/fancy_scripts'));
app.use('/fancy_scripts',  express.static(__dirname + '/fancy_scripts'));


app.use(function(req,res,next){
    req.db = db;
    next();
});

app.get('/', routes.index);

//var router = express.Router();
//
///* GET home page. */
//router.get('/', routes.index);

If were to guess the line app.use(app.router);

might be the culprit...?