diff --git a/src/math/random-data-generator/RandomDataGenerator.js b/src/math/random-data-generator/RandomDataGenerator.js
index ac3775dc6..b2637cb39 100644
--- a/src/math/random-data-generator/RandomDataGenerator.js
+++ b/src/math/random-data-generator/RandomDataGenerator.js
@@ -390,7 +390,7 @@ var RandomDataGenerator = new Class({
      */
     weightedPick: function (array)
     {
-        return array[~~(Math.pow(this.frac(), 2) * array.length + 0.5)];
+        return array[~~(Math.pow(this.frac(), 2) * (array.length - 0.5) + 0.5)];
     },
 
     /**