EmberJS: Observing JavaScript object's getter in computed properties

I have a JavaScript object with dynamically computed properties (using getter and setters), returned by a third party library and I want to observe them on my Ember computed properties.

If I pass such a property as a dependency in my computed property like below,

someProperty: computed('jsObject.property', function () {
    // Do something
})

Ember makes it undefined. Is this is bug in Ember or am I doing something wrong?