Ошибка is not a function

var express  = require('express'), 
    Recaptcha = require('recaptcha').Recaptcha; 
 
var PUBLIC_KEY  = '6LdtyzoUAAAAAFCPtAGGPlzjQC7pz7e2bFB1AHZj', 
    PRIVATE_KEY = '6LdtyzoUAAAAAN4aT1j5I3-x6kEaWuXkP2SgTs0G'; 
 
var app = express(); 
 
app.configure(function() { 
    app.use(express.bodyParser()); 
}); 
 
app.get('/', function(req, res) { 
    var recaptcha = new Recaptcha(PUBLIC_KEY, PRIVATE_KEY); 
 
    res.render('form.jade', { 
        layout: false, 
        locals: { 
            recaptcha_form: recaptcha.toHTML() 
        } 
    }); 
}); 
 
app.post('/', function(req, res) { 
    var data = { 
        remoteip:  req.connection.remoteAddress, 
        response:  req.body['g-recaptcha-response'] 
    }; 
    var recaptcha = new Recaptcha(PUBLIC_KEY, PRIVATE_KEY, data); 
 
    recaptcha.verify(function(success, error_code) { 
        if (success) { 
            res.send('Recaptcha response valid.'); 
        } 
        else { 
            // Redisplay the form. 
            res.render('form.jade', { 
                layout: false, 
                locals: { 
                    recaptcha_form: recaptcha.toHTML() 
                } 
            }); 
        } 
    }); 
}); 
 
app.listen(3000);