diff --git a/content/collections3.html b/content/collections3.html
index 105ac80..988a15f 100644
--- a/content/collections3.html
+++ b/content/collections3.html
@@ -73,7 +73,7 @@ <h2>Storing Models and emitting events</h2>
 </pre>
 
 <pre class="prettyprint">
-Collection.prototype.all = function() { return this._items; };
+Collection.prototype.all = function() { return this._items.slice(); };
 </pre>
 
 <h2>Iteration</h2>