Update Build

dist/leaflet.markercluster-src.js

@@ -586,6 +586,7 @@ L.MarkerCluster = L.Marker.extend({
 	},
 
 	_addChild: function (new1) {
+		this._expandBounds(new1);
 		if (new1 instanceof L.MarkerCluster) {
 			this._childClusters.push(new1);
 			this._childCount += new1._childCount;
@@ -598,18 +599,31 @@ L.MarkerCluster = L.Marker.extend({
 			this.setIcon(this._group.options.iconCreateFunction(this._childCount));
 		}
 
-		this._expandBounds(new1);
 	},
 
 	_expandBounds: function (marker) {
 
+		var addedCount,
+		    addedLatLng;
+
 		if (marker instanceof L.MarkerCluster) {
 			this._bounds.extend(marker._bounds);
+			addedCount = marker._childCount;
+			addedLatLng = marker._latlng;
 		} else {
-			this._bounds.extend(marker.getLatLng());
+			addedLatLng = marker.getLatLng();
+			this._bounds.extend(addedLatLng);
+			addedCount = 1;
 		}
 
-		this._latlng = this._bounds.getCenter();
+		var totalCount = this._childCount + addedCount;
+
+		if (!this._latlng) {
+			this._latlng = new L.LatLng(addedLatLng.lat, addedLatLng.lng);
+		} else {
+			this._latlng.lat = (addedLatLng.lat * addedCount + this._latlng.lat * this._childCount) / totalCount;
+			this._latlng.lng = (addedLatLng.lng * addedCount + this._latlng.lng * this._childCount) / totalCount;
+		}
 	},
 
 	//Set our markers position as given and add it to the map
@@ -1003,6 +1017,7 @@ L.MarkerCluster = L.Marker.extend({
 });
 
 
+
 L.DistanceGrid = function (cellSize) {
 	this._cellSize = cellSize;
 	this._sqCellSize = cellSize * cellSize;