GroupBox: title gets truncated

import QtQuick 2.1
import QtQuick.Controls 1.0
import QtQuick.Layouts 1.0

Column{
    width: 600
    height: 360

    GroupBox {
        width: parent.width
        checkable: true
        title: "this is a very very very very very very very very very very very very long text"
        Component.onCompleted: print("width " + implicitWidth)
        CheckBox {
            text: "A"
        }
    }

    GroupBox {
        width: parent.width
        checkable: true
        title: "This is a long long long long long long long text"
        CheckBox {
            text: "A"
        }
    }

    GroupBox {
        width: parent.width
        checkable: false
        title: "truncated too :("
        CheckBox {
            text: "A"
        }
    }

    GroupBox {
        width: parent.width
        checkable: false
        title: "Hello :)"
        CheckBox {
            text: "A"
        }
    }
}