Wrong Z order with DropShadow in WebAssembly

import QtQuick 2.15
import QtQuick.Window 2.15
import QtGraphicalEffects 1.15Window {
    id: root    
    width: 300
    height: 300    
    visible: true    
    
    Rectangle {
        id: header
        width: parent.width
        height: 50
        color: "#dddddd"
        visible: false
    }    
    
    DropShadow {
        anchors.fill: header
        horizontalOffset: 0
        verticalOffset: 1
        radius: 5
        samples: 11
        color: "#60000000"
        source: header
    }    
    
    Rectangle {
        id: bkg
        anchors { topMargin: header.height; fill: parent }
        color: "red"        
        
        Rectangle {
            width: parent.width
            height: 50
            color: "green"            
            
            Text {
                anchors.fill: parent
                text: "Hello World"
                color: "white"
            }
        }
    }    
    
    MouseArea {
        anchors.fill: parent
        onClicked: bkg.opacity = bkg.opacity === 0.5 ? 1 : 0.5
    }
}