EmberJs, changedAttributes() is not showing changes in the nested keys of a Hash attribute

The object is DS.Model:

$E.toString()
> "<reports-dashboard-client-app@model:report::ember596:914fc1b0-b14d-0133-bce2-68a86d03d830>"

The attribute is a Hash:

// app/models/report.js
export default DS.Model.extend({
  filters: DS.attr(),
  ...
});

This is how it looks like now:

$E.get('filters')
> Object {__ember_meta__: Meta}
>   __ember_meta__: Meta
>   age_groups: (...)
>   get age_groups: GETTER_FUNCTION()
>   set age_groups: SETTER_FUNCTION(value)
>   genders: (...)
>   get genders: GETTER_FUNCTION()
>   set genders: SETTER_FUNCTION(value)
>   __proto__: Object

There is not any change in the Model:

$E.changedAttributes()
> ember$data$lib$system$empty$object$$EmptyObject {}

I modify one of the Hash keys but still not change in the Model:

$E.get('filters.age_groups')
> ["21-30", "31-40"]
$E.set('filters.age_groups', ["21-30"])
> ["21-30"]
$E.changedAttributes()
> ember$data$lib$system$empty$object$$EmptyObject {}

Only if I change the Hash it self I obtain a change in the Model:

$E.set('filters', {})
> Object {}
$E.changedAttributes()
> ember$data$lib$system$empty$object$$EmptyObject {filters: Array[2]}

What is curious is that I can observe the property filters.age_groups and the Observer is triggered properly when this key has a change.

How can I check if there is any change in the nested keys of DS.Model attribute which is a Hash?