Is there any bug in required validation or ionic checkbox?

I have this code for checkbox and below I want to validate these checkboxes by selecting at least 1 checked. It looks like the required is not working in this case. Any ideas?

I’m appreciated you feedback.

<ion-checkbox name="routine" ng-repeat="item in routines"
                      ng-model="item.checked" 
                      ng-checked="item.checked"
                      ng-required="true">
          {{ item.name }}
        </ion-checkbox>

Please ignore this. The ng-required mainly is for the checkboxes that you need to select all of them. If you need to check only minimum you have to do different way which is:

setup on these in the controller:

$scope.routineCount = 0;
    $scope.routineCheck = function(routine) {
      if(routine.checked){
        $scope.routineCount--;//opposite
      }else{
        $scope.routineCount++;
      }
      console.log('routineCount: ' + routineCount);
    };

then in your html:

<label class="item item-input">Routines</label>
        <ion-checkbox name="routine" ng-repeat="item in routines"
                      ng-model="item.checked" 
                      ng-checked="item.checked"
                      ng-change="routineCheck(item)">
          {{ item.name }}
        </ion-checkbox>
        <span class="error text-danger" ng-show="routineCount==0">* checked one routine at least</span>
<button class="button button-full button-positive" ng-disabled="programAddForm.$invalid || routineCount==0">Save</button>