File Upload works with http but not with https

server.js

var fs = require('fs'),
  https = require('https'),
  express = require('express'),
  app = express(),
  multer = require('multer');

var storage = multer.diskStorage({
    destination: function(req, file, cb) {
        cb(null, '/tmp/');
    },
    filename: function(req, file, cb) {
        cb(null, file.originalname);
    }
});

var upload = multer({
    storage: storage
});

// Serve static files
app.use(express.static("./"));

// Create a https server
https.createServer({
  key: fs.readFileSync('key.pem'),
  cert: fs.readFileSync('cert.pem')
}, app).listen(55555);

app.get('/', function (req, res) {
  res.header('Content-type', 'text/html');
  return res.end('<h1>Hello, Secure World!</h1>');
});

// Post route
app.post('/upload/file', upload.single("upload"), function(req, res) {

    if (req.file) {
        res.send("Upload complete");
        res.end();
    } else {
        res.send("No file");
        res.end();
    }

});