LocalStrategy function never called

I have tried to setup a simple local strategy authentification with express4 / passportjs, but the authenticate function is never called : here's my code

var passport = require('passport');
var LocalStrategy = require('passport-local').Strategy;
app.use(compress());  
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());

/*  AUTHENTIFICATION */

app.use(passport.initialize());
app.use(passport.session());


passport.serializeUser(function(user, done) {
  done(null, user);
});

passport.deserializeUser(function(user, done) {
  done(null, user);
});

passport.use(new LocalStrategy(
  function(username, password, done) { //THIS FUNCTION IS NEVER CALLED
    console.log("Local strategy");
  }
));


app.post('/login', function(req, res) {
    console.log("user : ", req.body.username);
    console.log("password : ", req.body.password);
    passport.authenticate('local', { successRedirect: '/',
                                     failureRedirect: '/login' })
});

/*  !AUTHENTIFICATION */

app.use(express.static(path.join(__dirname, 'public')));
app.use(express.static(path.join(__dirname, 'bower_components')));
app.use(express.static(path.join(__dirname, 'controllers')));
app.use(express.static(path.join(__dirname, 'modules')));
app.use('/', routes);
app.use('/users', users);

When i send a post request in /login, i see in the logs the username and password but the password.authentificate method doesnt do anything. It should call the LocalStrategy function and console.log('strategy') but it doesn't.

Does someone know how to fix it ?

Thanks