diff --git a/CHANGELOG b/CHANGELOG
index aff192b..4f1af37 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Fix Class.mixin to extend the class's prototype.  [Mislav Marohnić]
+
 * Fix superclass method call breakage from [7337].  [Mislav Marohnić, sam]
 
 * Change Class.extend to allow for superclass method resolution and remove Class.inherit.  Closes #9274.  [Samuel Lebeau]
diff --git a/src/base.js b/src/base.js
index 9bb02ea..597a78f 100644
--- a/src/base.js
+++ b/src/base.js
@@ -48,7 +48,7 @@ var Class = {
   },
 
   mixin: function(destination, source) {
-    return Object.extend(destination, source);
+    return Object.extend(destination.prototype, source);
   }
 };