diff --git a/index.html b/index.html
index fc3134d..dcf5fd4 100644
--- a/index.html
+++ b/index.html
@@ -172,7 +172,7 @@ <h4>extend - processing option</h4>
         There is also this alternate syntax if you need to do unmapping:
         <pre><code>
 options:{ 
-    custom:{
+    extend:{
         "{root}.users[i]": {
             map:function(mapped){
                 mapped.isDeleted= ko.observable(false);