Realm Swift SUBQUERY について

よろしくお願いします。
iOS 8.0
Swift 2.1
Realm 0.96.3

親子関係を持つ二つのクラスを定義し、status が true の Child を一つ以上持つ Parent を抽出したいと思っています。

class Child: Object {
    dynamic var status = false
    dynamic var name = ""
    convenience init(name: String) {
        self.init()
        self.name = name
    }
}

class Parent: Object {
    let children = List<Child>()
    dynamic var name = ""
    convenience init(name: String) {
        self.init()
        self.name = name
    }
}

class ViewController: UIViewController {

    let realm = try! Realm()

    override func viewDidLoad() {
        super.viewDidLoad()
        setSampleData()
        procedure()
    }

    func procedure() {
        let predicate = NSPredicate(format: "SUBQUERY(children, $c, $c.status == true).@count > 0")
        print(realm.objects(Parent).filter(predicate).description)
    }

    func setSampleData() {
        try! realm.write {
            self.realm.deleteAll()
            let parent1 = Parent(name: "Parent1")
            let parent2 = Parent(name: "Parent2")
            let parent3 = Parent(name: "Parent3")
            let child1  = Child(name:  "Child1")
            let child2  = Child(name:  "Child2")
            let child3  = Child(name:  "Child3")
            let child4  = Child(name:  "Child4")
            let child5  = Child(name:  "Child5")
            self.realm.add(parent1)
            self.realm.add(parent2)
            self.realm.add(parent3)
            self.realm.add(child1)
            self.realm.add(child2)
            self.realm.add(child3)
            self.realm.add(child4)
            self.realm.add(child5)
            child1.status = false
            child2.status = true
            child3.status = false
            child4.status = true
            child5.status = false
            parent1.children.append(child1)
            parent1.children.append(child2)
            parent2.children.append(child3)
            parent2.children.append(child4)
            parent3.children.append(child5)
        }
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

}

ビルドは成功しますが、以下のようなエラーが出ます。

Terminating app due to uncaught exception 'Invalid predicate expressions', reason: 'Predicate expressions must compare a keypath and another keypath or a constant value'

SUBQUERYについて理解ができていないと思いますが、
調べてもなかなかわかりません。
どなたかアドバイスを頂けますでしょうか。