Mapbox / Leaflet.Markercluster Bug Replication

HTML

<script src="http://api.tiles.mapbox.com/mapbox.js/v1.0.3/mapbox.js"></script>
<script src="http://dev.vinpin.com/data/js/leaflet.markercluster.js"></script>
<link rel="stylesheet" href="http://dev.vinpin.com/data/css/MarkerCluster.css">
<link rel="stylesheet" href="http://dev.vinpin.com/data/css/MarkerCluster.Default.css">
<link rel="stylesheet" href="http://api.tiles.mapbox.com/mapbox.js/v1.0.3/mapbox.css">
<div id="map" style="height: 300px"></div>

JavaScript

var map = L.mapbox.map('map', 'vinpinr.map-atckgbg8');

var markers = new L.MarkerClusterGroup();

var json = [
    {
        type: 'Feature',
        geometry: {
            type: 'Point',
            coordinates: [-28, 49]
        },
        properties: {}
    },
    {
        type: 'Feature',
        geometry: {
            type: 'Point',
            coordinates: [-18, 49]
        },
        properties: {}
    },
    {
        type: 'Feature',
        geometry: {
            type: 'Point',
            coordinates: [-38, 49]
        },
        properties: {}
    }
];

for (var i = 0; i < json.length; i++) {
    var item = json[i];
    
    var marker = {
        type: 'Feature',
        geometry: {
            type: 'Point',
            coordinates: [item.geometry.coordinates[0], item.geometry.coordinates[1]]
        },
        properties: {}
    };
    
    var randomNumber = new Date().getTime();
    
    marker.properties.title = 'title ' + randomNumber;
    marker.properties.description = 'description ' + randomNumber;
    
    var markerObject = L.mapbox.markerLayer(marker);
    
    // Add to cluster
    markers.addLayer(markerObject);
}

map.addLayer(markers);

markers.eachLayer(function(marker) {
    // This (in my case) is always the same, but not here :(
    console.log(marker.feature.properties.title);
});