AngularJS NaN binding bug

HTML

<script src="http://ci.angularjs.org/view/AngularJS/job/angular.js-angular-master/3034/artifact/build/angular.js"></script>
<div ng-controller="MainController">
    <button ng-click="random1()">Random (controller)</button>
    
    {{ myNumber1 }}
</div>

<my-directive number="myNumber2"></my-directive>

{{ myNumber2 }}

JavaScript

var app = angular.module('myApp', []);

app.controller("MainController", function ($scope) {
    $scope.myNumber1 = NaN;
    
    $scope.random1 = function () {
        $scope.myNumber1 = Math.floor(Math.random() * 100);
    };
});

app.directive("myDirective", function () {
  return {
      template: "<button ng-click='random2()'>Random (directive)</button>",
      scope: {
          number: "="
      },
      link: function (scope, element, attrs) {
         andba //Comment this line and the binding will work.
          scope.number = NaN;
          
          scope.random2 = function () {
              scope.number = Math.floor(Math.random() * 100);
          };
      }
  };
});