angularjs unsub from events on $scope change

gistfile1.js

angular
    .module('MyApp')
    .config(['$provide', function($provide){
        $provide.decorator('$rootScope', ['$delegate', function($delegate){

            $delegate.constructor.prototype.$onRootScope = function(name, listener){
                var unsubscribe = $delegate.$on(name, listener);
                this.$on('$destroy', unsubscribe);
            };

            return $delegate;
        }]);
    }]);

found here: angular/angular.js#4574