Checking if a checkbox is disabled using isDisabled() returns false even when the checkbox really is disabled.

I looked through the code and I think the problem is this line because when I dumped the ChoiceFormField checkbox object this is what I got:

['options':private] =>
    array {
        array {
            'value' => 1,
            'disabled' => true
        }
    }
['value':protected] =>
    null

So obviously this $option['value'] == $this->value is false..
If when building the form I add an option 'value' => null to the checkbox form it works just fine.

Shouldn't the checkbox isDisabled function be different than the one for other choice inputs?