Android : Cordova: Pause event not firing

For some reason the pause event is not firing when it should.

If I press the home button on my phone, this is where the pause event should be fired, which should pause the music. But instead it keeps on playing it.

But when I open my app again it is suddenly paused and then resumed. So it fires both events when I return to the app.

Why is onPause not firing when I leave the app?

I have the following code:

function onLoad() {
    document.addEventListener("deviceready", onDeviceReady, false);

function onDeviceReady() {
    document.addEventListener("resume", onResume, false);
    document.addEventListener("pause", onPause, false);
}

function onPause() {
    PauseMusic();
    alert('paused');
}

function onResume() {
    ResumeMusic();
    alert('resumed');
}