Passport Unknown authentication strategy

I am following this tutorial on creating an authentication system with passport in Nodejs

Currently I am trying to make the signup form work, but it gives this error:

Error: Unknown authentication strategy "local-signup"
    at attempt (/home/jarno/0__projects/nodejs/EasyOrders_2.3.0/node_modules/passport/lib/middleware/authenticate.js:173:37)
    at authenticate (/home/jarno/0__projects/nodejs/EasyOrders_2.3.0/node_modules/passport/lib/middleware/authenticate.js:349:7)
    at Layer.handle [as handle_request] (/home/jarno/0__projects/nodejs/EasyOrders_2.3.0/node_modules/express/lib/router/layer.js:95:5)
    at next (/home/jarno/0__projects/nodejs/EasyOrders_2.3.0/node_modules...

I am pretty sure that the config/passport.js file isn't seen by the routes/users.js file, but as I am a beginner I can't seem to find a solution to my problem.

/routes/users.js

var express = require('express');
var router = express.Router();
var passport = require('passport');
require('../config/passport');


/* GET users listing. */
router.get('/login', function(req, res){
  res.render('login', {
    title: 'Login'
  });
});

router.get('/signup', function(req, res){
  res.render('signup', {
    title: 'signup'
  });
});

router.get('/logout', function(req, res){
  res.logout();
  res.redirect('/users/login')
});

/* POST users listing */
router.post('/signup', passport.authenticate('local-signup', {
  successRedirect : '/profile', // redirect to the secure profile section
  failureRedirect : '/signup', // redirect back to the signup page if there is an error
  failureFlash : true // allow flash messages
}));


/* functions */
function isLoggedIn(req, res, next) {

  if (req.isAuthenticated())
    return next();

  res.redirect('/users/login');
}



module.exports = router;

/config/passport.js

// config/passport.js
var passport = require('passport');
// load all the things we need
var LocalStrategy   = require('passport-local').Strategy;

// load up the user model
var User            = require('../models/user');

// expose this function to our app using module.exports
module.exports = function(passport) {

    // =========================================================================
    // passport session setup ==================================================
    // =========================================================================
    // required for persistent login sessions
    // passport needs ability to serialize and unserialize users out of session

    // used to serialize the user for the session
    passport.serializeUser(function(user, done) {
        done(null, user.id);
    });

    // used to deserialize the user
    passport.deserializeUser(function(id, done) {
        User.findById(id, function(err, user) {
            done(err, user);
        });
    });

    // =========================================================================
    // LOCAL SIGNUP ============================================================
    // =========================================================================
    // we are using named strategies since we have one for login and one for signup
    // by default, if there was no name, it would just be called 'local'

    passport.use('local-signup', new LocalStrategy({
        // by default, local strategy uses username and password, we will override with email
        usernameField : 'email',
        passwordField : 'password',
        passReqToCallback : true // allows us to pass back the entire request to the callback
    },
      function(req, email, password, done) {

          // asynchronous
          // User.findOne wont fire unless data is sent back
          process.nextTick(function() {

          // find a user whose email is the same as the forms email
          // we are checking to see if the user trying to login already exists
            User.findOne({ 'local.email' :  email }, function(err, user) {
                // if there are any errors, return the error
                if (err)
                    return done(err);

                // check to see if theres already a user with that email
                if (user) {
                    return done(null, false, req.flash('signupMessage', 'That email is already taken.'));
                } else {

                    // if there is no user with that email
                    // create the user
                    var newUser            = new User();

                    // set the user's local credentials
                    newUser.local.email    = email;
                    newUser.local.password = newUser.generateHash(password);

                    // save the user
                    newUser.save(function(err) {
                        if (err)
                            throw err;
                        return done(null, newUser);
                    });
                }

            });

            });

      }));

};

/app.js

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



var mongoose = require('mongoose');
var passport = require('passport');
var flash = require('connect-flash');
var morgan = require('morgan');
var session = require('express-session');

var configDB = require('./config/database.js');

mongoose.connect(configDB.url);
require('./config/passport');

// init app
var app = express();
var index = require('./routes/index');
var users = require('./routes/users');

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');

// uncomment after placing your favicon in /public
//app.use(favicon(path.join(__dirname, 'public', 'favicon.ico')));
app.use(logger('dev'));
app.use(morgan('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(require('stylus').middleware(path.join(__dirname, 'public')));
app.use(express.static(path.join(__dirname, 'public')));


app.use(session({ secret: 'godaddy420' })); // session secret
app.use(passport.initialize());
app.use(passport.session()); // persistent login sessions
app.use(flash()); // use connect-flash for flash messages stored in session


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




app.use('/', index);
app.use('/users', users);

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  var err = new Error('Not Found');
  err.status = 404;
  next(err);
});

// error handler
app.use(function(err, req, res, next) {
  // set locals, only providing error in development
  res.locals.message = err.message;
  res.locals.error = req.app.get('env') === 'development' ? err : {};

  // render the error page
  res.status(err.status || 500);
  res.render('error');
});

module.exports = app;

via DowinskiField