Adding ApplicationTrigger task in UWP package manifest declarations cannot compile

I am trying to use the following:

private async void RunBackgroundTask()
    {
        string entryPoint = "BackgroundTask.AudioBackgroundTask";
        string taskName = "task";
        ApplicationTrigger trigger = new ApplicationTrigger();
        BackgroundTaskRegistration task = RegisterBackgroundTask(entryPoint, taskName, trigger, null);
        await Task.Delay(1000);
        var result = await trigger.RequestAsync();
    }

If I try to use as is I receive in the result an UnknownError, and I think is because I have to add the Task systemEvent in the declarations as following:

<Extensions>
    <Extension Category="windows.backgroundTasks" EntryPoint="BackgroundTask.AudioBackgroundTask">
      <BackgroundTasks>
        <Task Type="audio" />
        <Task Type="systemEvent" />
      </BackgroundTasks>
    </Extension>
  </Extensions>

But surprise is no longer supported, I receive the following error:

Severity Code Description Project File Line Suppression State Error Error : DEP0700 : Registration of the app failed. AppxManifest.xml(32,10): error 0x80080204: Cannot register the e77f1d84-cd41-4053-8a84-2db36d0cbd8e_1.0.0.0_x86__dy4sgpjxhat8m package because the extension is missing an EntryPoint or StartPage attribute. (0x80073cf6) BackgroundAudioGraph

I have also set all the application and the task to 10240 but the same, how can be possible because I saw even in @Jerrynixon example:

https://github.com/Windows-XAML/201505-Ignite/blob/master/BackgroundTask/MyApp/Package.appxmanifest

the systemEvent declared task, so I do not know how to follow.

Thanks!