Initial readonly property is not set when using Loader.setSource

import QtQuick 2.12
import QtQuick.Window 2.12

Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")

    Component.onCompleted: loader.setSource("qrc:/RectTest.qml", {  "text": "asasas"})
    Loader {
        id: loader
        anchors.fill: parent
    }
}

//RectTest.qml
import QtQuick 2.0

Rectangle {
    id:root
    color: "orange"
    readonly property string text: ""

    Text {
        text:root.text
        color: "white"
        anchors.centerIn: parent
    }

}