diff --git a/lib/mbtiles.js b/lib/mbtiles.js
index 3968eb7..7bfe54c 100644
--- a/lib/mbtiles.js
+++ b/lib/mbtiles.js
@@ -76,7 +76,7 @@ MBTiles.prototype._open = function(uri) {
 
     var key = url.format(uri);
     this.filename = uri.pathname;
-    this._batchSize = uri.query.batch;
+    this._batchSize = +uri.query.batch;
     Step(function() {
         mbtiles._db = new sqlite3.Database(mbtiles.filename, this);
     }, function(err) {