TypeError: Cannot read property 'service' of undefined

app.js

import Feathers from 'feathers';
// ...

let app = Feathers();

app
    .use(compress())
    .options('*', cors())
    .use(cors())
    .use(BodyParser.json())
    .use(BodyParser.urlencoded({extended: true}))
    .configure(Hooks())
    .configure(Rest())
    .configure(SocketIO())
    .configure(Authentication({}));
    
app.use('/users', MongooseService({
    Model: Models.User
}));
const Users = app.service('users');
Users.before({
    create: [AppHooks.Users.create(), AuthenticationHooks.hashPassword()],
    find: [AuthenticationHooks.verifyToken(), AuthenticationHooks.populateUser()],
    get: [AuthenticationHooks.verifyToken(), AuthenticationHooks.populateUser()],
    update: [AuthenticationHooks.hashPassword(), AuthenticationHooks.verifyToken(), AuthenticationHooks.populateUser(), AuthenticationHooks.requireAuth(), AppHooks.Users.usersCanOnlyModifyThemselves(Users)],
    patch: [AuthenticationHooks.hashPassword(), AuthenticationHooks.verifyToken(), AuthenticationHooks.populateUser(), AuthenticationHooks.requireAuth(), AppHooks.Users.usersCanOnlyModifyThemselves(Users)],
    remove: [AuthenticationHooks.verifyToken(), AuthenticationHooks.populateUser(), AuthenticationHooks.requireAuth(), AppHooks.Users.usersCanOnlyModifyThemselves(Users)]
}).after({
    all: [MongooseService.hooks.toObject(), AppHooks.Users.hidePassword]
});
// ...

export default app;

server.js

#!/usr/bin/env node

// ../build/app is my Babel output dir
var app = require('../build/app');

var port = normalizePort(process.env.PORT || '3000');
app.listen(port);
console.log(`Listening on ${port}`);

function normalizePort(val) {
    var port = parseInt(val, 10);

    if (isNaN(port)) {
        // named pipe
        return val;
    }

    if (port >= 0) {
        // port number
        return port;
    }

    return false;
}