VueJs: Error with server side rendering and Typescript

I am trying to build a stack using Server Side Rendering (SSR) and Typescript. Everything seems fine but I got the error: TypeError: Cannot read property 'render' of undefined. Here is the full stack trace:

TypeError: Cannot read property 'render' of undefined
    at normalizeRender (/Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/vue-server-renderer/build.js:6621:19)
    at render (/Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/vue-server-renderer/build.js:6840:5)
    at Object.renderToString (/Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/vue-server-renderer/build.js:6871:9)
    at /Users/shoun/Documents/repositories/vuejs-ssr-typescript/dist/server.js:16:14
    at Layer.handle [as handle_request] (/Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/express/lib/router/layer.js:95:5)
    at next (/Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/express/lib/router/route.js:137:13)
    at Route.dispatch (/Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/express/lib/router/route.js:112:3)
    at Layer.handle [as handle_request] (/Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/express/lib/router/layer.js:95:5)
    at /Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/express/lib/router/index.js:281:22
    at param (/Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/express/lib/router/index.js:354:14)
TypeError: Cannot read property 'render' of undefined
    at normalizeRender (/Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/vue-server-renderer/build.js:6621:19)
    at render (/Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/vue-server-renderer/build.js:6840:5)
    at Object.renderToString (/Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/vue-server-renderer/build.js:6871:9)
    at /Users/shoun/Documents/repositories/vuejs-ssr-typescript/dist/server.js:16:14
    at Layer.handle [as handle_request] (/Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/express/lib/router/layer.js:95:5)
    at next (/Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/express/lib/router/route.js:137:13)
    at Route.dispatch (/Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/express/lib/router/route.js:112:3)
    at Layer.handle [as handle_request] (/Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/express/lib/router/layer.js:95:5)
    at /Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/express/lib/router/index.js:281:22
    at param (/Users/shoun/Documents/repositories/vuejs-ssr-typescript/node_modules/express/lib/router/index.js:354:14)

Here is my server configuration:

import * as express from 'express';
import * as path from 'path';
import * as VueRender from 'vue-server-renderer';
import * as fs from 'fs-extra';
import app from './assets/app';
declare var __dirname;

// Get the HTML layout
const layout = fs.readFileSync(path.join(__dirname, 'index.html'), 'utf8');

// Create a renderer
const renderer = VueRender.createRenderer();

let server = express();

server.get('/hello', function (req, res) {
    res.send('Hello World!');
});

server.use('/assets', express.static(path.join(__dirname, 'assets')));

// Handle all GET requests
server.get('*', function (request, response) {
    // Render our Vue app to a string
    renderer.renderToString(
        // Create an app instance
        app(),
        // Handle the rendered result
        function (error, html) {
            // If an error occurred while rendering...
            if (error) {
                // Log the error in the console
                console.error(error);
                // Tell the client something went wrong
                return response
                    .status(500)
                    .send('Server Error')
            }
            // Send the layout with the rendered app's HTML
            response.send(layout.replace('<div id="app"></div>', html))
        }
    )
});

let port = 4500;
server.listen(port, () => {
    console.log(`App listening on ${port}`);
});

You can find the source code on my github repository: https://github.com/sichida/vuejs-ssr-typescript. I could really use some help because I am stuck...

Thank you very much!

via Shoun