Support for the ng-disabled directive.

I'm having trouble to use this directive together with the ng-disabled directive (and form validation to disable the submit button when the form is invalid).
I created an example to show my issue: http://jsfiddle.net/jespermjonsson/bxste159/
The submit button isn't initially disabled even if the ng-disabled directive have disabled the button due to the disabled attribute is removed by ladda.stop().