Bluebird memory leak

.gitignore

node_modules

memoryleak.js

var Promise = require('bluebird'),
    express = require('express'),
    request = require('request'),
    step = require('step');

var app = express();

// test endpoint to test this request
app.post('/test', function(req, res) {
    res.json({success: true});
});

var server = app.listen(3000);

function make_request_normal(callback) {
    request.post({
        url: "http://localhost:3000/test",
        method: "POST",
        body: JSON.stringify({first_name: "Victor"})
    }, function(err, response, body) {
        callback(err, response, body);
    });
}

function make_request_with_step(callback) {
    step(
        function() {
            // noop
            this(null, 'test');
        },
        function(err, test) {
            request.post({
                url: "http://localhost:3000/test",
                method: "POST",
                body: JSON.stringify({first_name: "Victor"})
            }, this);
        },
        function(err, response, body) {
            callback(null, response, body);
        }
    );
}


// Works fine
// make_request(function(err, response) {
//     console.log(body);
//     server.close();
// });

// Blows up?
// Promise.promisify(make_request_normal)().spread(function(response, body) {
//     console.log(response);
//     console.log(body);
//     server.close();
// });


Promise.promisify(make_request_with_step)().spread(function(response, body) {
    console.log(body);
    server.close();
});

package.json

{
  "dependencies": {
    "bluebird": "~0.11.5-0",
    "request": "~2.33.0",
    "express": "~3.4.8",
    "step": "0.0.5"
  }
}