Client SSL on NodeJS always fails to authenticate

I'm following this tutorial to create a HTTPS server.

My app.js looks like:

var https = require('https');
//var httpServer = http.createServer(app);
//httpServer.listen(3000);
var options = {
    key:    fs.readFileSync('./config/ssl/server.key'),
    cert:   fs.readFileSync('./config/ssl/server.crt'),
    ca:     fs.readFileSync('./config/ssl/ca.crt'),
    requestCert:        true,
    rejectUnauthorized: false,
    passphrase: 'password'
};

https.createServer(options, app).listen(5000);

Some API calls, I want to ensure that the client provides the certificate, so I've done:

// List all boxes
router.get('/api/boxes', function(req, res, next) {
   if (req.client.authorized) {
        next();
   } else {
        res.writeHead(401, {"Content-Type": "application/json"});
        res.end('{"status": "denied"}');
   }
}, boxesController.list);

Then, I call my server with curl using:

curl -s -v -k --key ./client.key --cert ./client.crt https://10.0.1.13:5000/api/boxes

But it always returns {status: denied}. Why?