diff --git a/api/average().js b/api/average().js
index 41e095b..cb400d6 100644
--- a/api/average().js
+++ b/api/average().js
@@ -25,7 +25,7 @@ jQuery.fn.dataTable.Api.register( 'average()', function () {
     var data = this.flatten();
     var sum = data.reduce( function ( a, b ) {
         return (a*1) + (b*1); // cast values in-case they are strings
-    } );
+    }, 0 );
  
     return sum / data.length;
 } );