messagedialog does not show: Binding on contentItem is not deferred (...)

Ttberg

When I try to show a message dialog (using Qt 6.3 and ubuntu 20), I get the following error:
Binding on contentItem is not deferred as requested by the DeferredPropertyNames class info because one or more of its sub-objects contain an id

The following sample code replicates this issue:

Item {
    Rectangle {
        color: "blue"
        anchors.fill: parent

        Button {
            anchors.centerIn: parent
            width: 50
            height: 50
            onPressed: {
                messageDialogReady.open()
            }
        }

        MessageDialog {
            id: messageDialogReady
            title: "Ready"
            text: "The calibration procedure is ready. Press the save button to save this calibration"
            buttons: MessageDialog.Ok
            onAccepted: {
                close()
            }
        }
    }
}

what am I missing?