AngularJS directive require '^' returns controller on same element - not parent

(Solved in https://stackoverflow.com/a/19323406/462897 - Being a newbie (for stackoverflow) I can't answer my own question right now.)

The angular 1.2.14 compile docs say: '^ - Locate the required controller by searching the element's parents. Throw an error if not found.'

It seems to me that I not only get a controller on a parent element, but also controllers defined on the same element. Which isn't what is documented or what I need.

Any ideas what I'm doing wrong?

module.directive('viForm', [ViFormDirective]);
  function ViFormDirective () {
    return {
      restrict: 'A',
      require: ['form', 'viForm', '^viForm'],
      controller: [ViFormController],
      link: function ($scope, iElement, iAttrs, ctrls) {
        // ctrls[0] ngForm
        // ctrls[1] our ctrl           'viForm'
        // ctrls[2] parentViFormCtrl   '^viForm' - THIS is the same as ctrls[1]
        ctrls[1].setNgForm(ctrls[0]);
        $scope[ctrls[0].$name + 'ViForm'] = ctrls[1];


        // todo check why the ^ parent prefix isn't working
        if (ctrls[2] && ctrls[1] !== ctrls[2]) {
          ctrls[1].setParentForm(ctrls[2]);
        }
      }
    };
  }