Flickable::contentY is incorrect if Flickable is anchored to a non-root object and has top/bottom margins

import QtQuick 2.0

Item{      
    width: 569;  height: 762    
    
    Rectangle{//NO PROBLEM IF WE COMMENT THIS Rectangle OUT
        anchors.fill: parent
        
        ListView{
            id: listView
            
            anchors{fill: parent;  topMargin: 1}//NO PROBLEM WITH topMargin: 0
            onContentYChanged: print('onContentYChanged', contentY)
            
            model: 10
            
            delegate: Text{
                width: listView.width;  height: listView.height / 5            
                text: modelData
            }
            
            Rectangle{//scrollbar
                color: 'red'
                width: 0.01 * parent.width;  radius: width / 2
                anchors{right: parent.right;  margins: radius}
                height:  Math.max(parent.height / parent.contentHeight * parent.height - 2 * radius, 20)//minimum height for large lists
                y:       parent.contentY / parent.contentHeight * parent.height + radius
                visible: parent.height < parent.contentHeight
            }
        }
    }
}