Ion-radio first item checked

Is there a bug with the directive? I can't seem to set one radio button (inside a collection of radio buttons) to be checked..

I've tried everything, it just doesn't work...

Example im using:

         <div class="list list-inset"> 
            <ion-radio ng-repeat="r in radioButtons" ng-model="user.encryption" ng-checked="r.checked" ng-      value="r.value">  {{r.text}}</ion-radio>  
         </div>

and in controller:

     $scope.radioButtons = [
        {text: "No Encryption", value: "no_encryption", checked : "checked"},
        {text: "MD5", value: "md5_encryption"},
        {text: "SHA1", value: "sha1_encryption"},
     ];

The above is just one example i've tried, i've tried so many, even setting ng-checked="true" or "checked" manually.

Am i doing something wrong?

Thanks