diff --git a/code/simple-mvvm/yarn.lock b/code/simple-mvvm/yarn.lock
index 7f9ac31..d0bd768 100644
--- a/code/simple-mvvm/yarn.lock
+++ b/code/simple-mvvm/yarn.lock
@@ -15,8 +15,8 @@ abbrev@1:
   resolved "http://registry.npm.taobao.org/abbrev/download/abbrev-1.1.1.tgz#f8f2c887ad10bf67f634f005b6987fed3179aac8"
 
 acorn@^6.1.0:
-  version "6.1.0"
-  resolved "http://registry.npm.taobao.org/acorn/download/acorn-6.1.0.tgz#b0a3be31752c97a0f7013c5f4903b71a05db6818"
+  version "6.4.1"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.4.1.tgz#531e58ba3f51b9dacb9a6646ca4debf5b14ca474"
 
 ansi-regex@^2.0.0:
   version "2.1.1"