diff --git a/docs/class-extends.md b/docs/class-extends.md
index 3d39842..867868d 100644
--- a/docs/class-extends.md
+++ b/docs/class-extends.md
@@ -713,8 +713,8 @@ function mix(...mixins) {
   class Mix {}
 
   for (let mixin of mixins) {
-    copyProperties(Mix.prototype, new mixin()); // 拷贝实例属性
-    copyProperties(Mix.prototype, mixin.prototype); // 拷贝原型属性
+    copyProperties(Mix.prototype, mixin); // 拷贝实例属性
+    copyProperties(Mix.prototype, Object.getPrototypeOf(mixin)); // 拷贝原型属性
   }
 
   return Mix;