RadialGradient QML Type is not painted by the puppet

import QtQuick 2.12
import QtGraphicalEffects 1.12

Item {
    width: 300
    height: 300

    RadialGradient {
        anchors.fill: parent
        gradient: Gradient {
            GradientStop { position: 0.0; color: "white" }
            GradientStop { position: 0.5; color: "black" }
        }
    }
}