Binding doesn't seem to be released on changed 'when' property

import QtQuick
import QtQuick.Controls.Material

Window {
    id: win
    width: 640
    height: 480
    visible: true
    title: "Wohooooo"

    Component {
        id: sourceComponent1

        Item {
            property string moo
        }
    }

    Component {
        id: sourceComponent2

        Item {}
    }

    Loader {
        id: loader
        sourceComponent: sourceComponent1
    }

    Button {
        text: "Click me"
        onClicked: () => {
            loader.sourceComponent = sourceComponent2
        }
    }

    Binding {
        target: loader.item
        when: loader.item && loader.item.hasOwnProperty("moo")
        property: "moo"
        value: "42 is the answer"
    }
}