laravel - Laravel Elixir version rev-manifest incomplete on gulp default task

Question

I have my gulpfile (using Laravel Elixir) set up to create 4 files.

app.css    
app.js
vendor.css
vendor.js

When I run either gulp, or gulp default app.js does not get created. Yet if I run gulp watch, it is created perfectly.

Here is the elixir method:

elixir(function(mix) {
    // Register html watcher
    mix.templates()

    // Compile app css
    .sass('app.scss', null, {
        includePaths: require('node-bourbon')
            .with(require('node-neat').includePaths)
    })

    // Concatenate vendor css
    .styles([
        ...
    ], 'public/css/vendor.css', 'public/css/vendor')

    // Minify & concatenate vendor js
    .scripts([
        ...
    ], 'public/js/vendor.js', 'public/js/vendor')

    // Minify and concatenate app js
    .scriptsIn('resources/assets/js', 'public/js/app.js')

    // Version the compiled resources
    .version([
        'css/app.css',
        'js/app.js',
        'css/vendor.css',
        'js/vendor.js'
    ]);
});