FailureFlash with Passportjs and Express

Im trying to flash error messages on failed login (ExpressJS 4.2 and PassportJS)

My code is:

//Admin Route =====

router.get('/admin', function(req, res) {

    res.render('admin', {message: '', user: ''});

});
router.post('/admin', passport.authenticate('loginAdmin',{  successRedirect: '/panel',
                                                failureRedirect: '/admin',
                                                failureFlash: true })

);

//Passport local strategy =====

passport.use('loginAdmin', new LocalStrategy(

  function(username, password, done) {



    modeloUsuario.findOne({ nombre: username, password: password }, function(err, user) {



      if (err) { return done(err); }

      if (!user) {

        return done(null, false, {message: 'Incorrect username.'}); //Error to show
      }



      return done(null, user);
    });
  }
));

But "message" in get request of /admin never gets replaced with "Incorrect username." Am I doint it wrong? Thanks in advance!