Error Unknown method return type: QMediaPlaylist* passing *QMediaPlaylist from C++ to QML

Error type: Unknown method return type: QMediaPlaylist*
It happens when passing QMediaPlaylist* from C++ to QML.
The code is compose by a playlistModel that load automatically a playlist vector according to the folder found in the system. In QML the user select the playlist which gets loaded in MediaPlayer.

In QML the playlist model is shown with a pathView and one selected, its index is passed to a MediaPlayer as follow:

_import QtQuick 2.6
import QtQuick.Controls 2.0
import QtMultimedia 5.9
import "."

import "QUItMeterComponent"
import "../menu"

PageTheme {
property string playlistName
property int playlistIndex
property int playlistSize

id: musicPage
toolbarTitle: playlistName + ": " + playlistSize + " songs"

function changePlaylist() {
var item = playlistModel.getPlaylistFromIndex(playlistIndex)
//note: using double ! to check item is not null or undefined (little JavaScript trick)
if(!!item)

{ playMusic.playlist = item; console.log("playlist changed!!"); }

else
console.log("playlist no good!!");
}

onPlaylistIndexChanged: changePlaylist()

MediaPlayer

{ id: playMusic autoLoad: true autoPlay: true //Component.onCompleted: changePlaylist() }

_

In main.cpp playlistModel is created and made available to QML as follow:

_
PlayListModel playlistModel("/home/root");

QQmlApplicationEngine engine;

QQmlContext* context = engine.rootContext();
context->setContextProperty("playlistModel", &playlistModel);
_

Despite Q_DECLARE_METATYPE(QMediaPlaylist*) is declared, I got the error.