PlaylistItem not working with properties

[Marko Stanke]

This works:

Audio {
        id: player;
        playlist: Playlist {
            id: playlist
            PlaylistItem {
                source: "...fullpath/Media/Audio/audio1.mp3" }
        }
    }

This doesn't work:

Audio {
        id: player;
        playlist: Playlist {
            id: playlist
            PlaylistItem {
                property url test: "...fullpath/Media/Audio/audio1.mp3"
                source: test  }
        }
    }

I really don't understand why. Could somebody explain this behaviour and how to fix this problem?