How to change class on checked multiple checkboxes in AngularJS

I hove some list of checkboxes, they're in classic ng-repeat. I wish to change class of label on checking my checkboxes individually. Right now i have all checkboxes with checked class. What is wrong?

<fieldset class="g-checkbox_square_big box-inline-full_width-relative">
    <label class="box-full_width-grid-vertical_align_middle" ng-class="{checked: 'area_selected_' + area.id}">
        <div class="g-checkbox-dummy"></div>
        <img src="" class="shift-padding_2-horizontal" alt="Area Image">
        <span class="text-size_big-color_appblue"></span>
    </label>
    <input type="checkbox" ng-bind-model="'area_selected_' + area.id" data-id=""/>
</fieldset>

FYI : The input is covering all dummy checkbox space.