diff --git a/lib/natural/util/bag.js b/lib/natural/util/bag.js
index c5ddb3c25..360d90e24 100644
--- a/lib/natural/util/bag.js
+++ b/lib/natural/util/bag.js
@@ -28,6 +28,7 @@ function Bag() {
 
 Bag.prototype.add = function(element) {
     this.dictionary.push(element);
+    this.nElement++;
     return this;
 };