Leaflet & Mapbox: OpenPopup not working

I've an issue with the leaflet openPopup method.

showMap = function(elements) {
    var jsonp = 'http://a.tiles.mapbox.com/v3/blahblahblah.jsonp';
    var m = new L.Map("my_map").setView(new L.LatLng(51.5, -0.09), 15);

    var geojsonLayer = new L.GeoJSON();

    var PlaceIcon = L.Icon.extend({
        iconSize: new L.Point(25, 41),
        shadowSize: new L.Point(40, 35),
        popupAnchor: new L.Point(0, -30)
    });

    var icon = new PlaceIcon(__HOME__ + '/images/leaflet/marker.png');
    var marker;


    for (var i = 0; i < elements.length; i++) {
        var address = $("<div/>").html(elements[i].address).text();
        var latlng = new L.LatLng(elements[i].latitude, elements[i].longitude);
        marker = new L.Marker(latlng, {icon: icon}).bindPopup(address);

        if (i == 0) {
            marker.openPopup();
        }
        m.addLayer(geojsonLayer).addLayer(marker);
    }
    // Get metadata about the map from MapBox
    wax.tilejson(jsonp, function(tilejson) {
        m.addLayer(new wax.leaf.connector(tilejson));
    });
}

When I click on a marker I have the popup open. But I would like to have the first popup open when the map is loaded. (and open other popups on markers click)

AnNy ideas ?