Angular ng-class re-evaulate

Im using ng-class to apply the class active when collapseSidebar is set to true revealing my sidebar.

<div class="row full-height row-offcanvas row-offcanvas-left" ng-class="{active: collapseSidebar}">
    <div id="sidebar" class="col-sm-4 col-md-3 col-lg-3 col-xl-2 sidebar-offcanvas">
    </div>

js

$scope.collapseSidebar = false;

    $scope.select = function(thing)
    {
        $scope.selectedThing = (thing !== $scope.selectedThing) ? thing : null;
        $scope.collapseSidebar = true;
    };

However the sidebar can be hidden in other ways (click a menu icon in the top left) removing the class active. When I call select(thing) I was hoping that ng-class would be re-evaluated and the class 'active' would be re-applied, however this does not happen, I have tried setting it to false and then straight back to true which also didn't work.

How can I get ng-class to re-evaluate collapseSidebar and apply 'active' even if the value is the same as be