Ember computed properly not firing on property change

I'm having a weird issue where a computed property isn't firing when it's dependent properties change.

Computed Property and Actions

answers: computed('variant.questionAnswers.[]', function() {
  return get(this, 'variant.questionAnswers').sortBy('position');
}),

...

actions: {
  reorderItems(answerModels) {
    answerModels.forEach(function(item, index) {
      set(item, 'position', index + 1);
    });
  }
}

The answerModels in the action is an array of all the answers, and setting the position works properly in that action. I can see the position changing in the ember inspector as well as when I inspect the individual models.

However, it does not update the view order because the answers computed property does not get fired.

I've tried changing the dependent property to variant.questionAnswers, variant.questionAnswers.@each.position, variant.questionAnswers.[], but nothing seem to fire when I change the position in the action.

How I got around it was add a timeHack attribute that makes it work, but obviously is not ideal...

timeHack: null,

answers: computed('timeHack', 'variant.questionAnswers.[]', function() {
  return get(this, 'variant.questionAnswers').sortBy('position');
}),

actions: {
  reorderItems(answerModels) {
    answerModels.forEach(function(item, index) {
      set(item, 'position', index + 1);
    });
    set(this, 'timeHack', new Date());
  }
}

Any thoughts on how to get this to work?