How to set false value to ng-model when my checkbox is not selected

I want to have false value when user checkbox is not checked.
HTML Code

On checking the checkbox value is setting as 'true' in addUser.isAllOrgSelected. But when checkbox is not checked value is not getting set to 'false'.

           <input type="checkbox" id="checkbox-1-1" class="regular-checkbox" 
           ng-true-value="true" ng-false-value="false" ng-
             model="addUser.isAllOrgSelected">
                 <label for="checkbox-1-1"></label>
               <span class="check-text">ALL</span>