ngRepeater bug

HTML

<script src="http://ci.angularjs.org/job/angular.js-pete/12/artifact/build/angular.js"></script>
<div ng:app>
 <div ng-controller="Ctrl">
   <div ng-repeat="(letter, number) in obj">
       {{letter}} and {{number}}
         <input type="checkbox" ng-model="obj[letter]">
   </div>
 </div>
</div>

CSS

.ng-invalid { border: 1px solid red; } 
body { font-family: Arial,Helvetica,sans-serif; }
body, td, th { font-size: 14px; margin: 0; }
table { border-collapse: separate; border-spacing: 2px; display: table; margin-bottom: 0; margin-top: 0; -moz-box-sizing: border-box; text-indent: 0; }
a:link, a:visited, a:hover { color: #5D6DB6; text-decoration: none; }
.error { color: red; }

JavaScript

function Ctrl($scope) {
    $scope.obj = {
        a: true,
        b: true,
        c: true
    };
}