Cannot read property 'toString' of undefined

router.post('/signUp', function(req, res, next) {
    userPhoto = req.files.photo;
    console.log(userPhoto.name);                    // 9cI4a4JQr5g.jpg
    console.log(typeof(userPhoto));                 // object
    console.log(userPhoto.name);                    // 9cI4a4JQr5g.jpg
    console.log(typeof(userPhoto));                 // object
    console.log(userPhoto.name.toString());         // 9cI4a4JQr5g.jpg
    console.log(typeof(userPhoto.name.toString())); // string
    var superPath = userPhoto.name.toString();
    var path = (dir + "/" + userPhoto.name).toString();
    fs.rename(superPath.path.toString(), path, function(err){ // 35:27
      if (err) throw err;
      console.log('photo upload');
    });
    req.session.firstName = req.body.firstName;
    req.session.lastName = req.body.lastName;
    req.session.age = req.body.age;
    req.session.skill = req.body.skill;
    firstName = req.session.firstName;
    lastName = req.session.lastName;
    age = req.session.age;
    skill = req.session.skill;
    console.log(userPhoto);
    res.redirect('/main');
});

TypeError: Cannot read property 'toString' of undefined at c:\Users\Администратор\Desktop\project\routes\index.js:35:27