diff --git a/docs/zh-cn.md b/docs/zh-cn.md
index fa16afd5..090b2f90 100644
--- a/docs/zh-cn.md
+++ b/docs/zh-cn.md
@@ -75,7 +75,7 @@ docsify serve docs
 <link rel="stylesheet" href="//unpkg.com/docsify/themes/buble.css">
 ```
 
-### 压缩版
+压缩版
 
 ```html
 <link rel="stylesheet" href="//unpkg.com/docsify/lib/themes/vue.css">
diff --git a/src/render.js b/src/render.js
index 0d8553df..83847579 100644
--- a/src/render.js
+++ b/src/render.js
@@ -27,7 +27,7 @@ renderer.heading = function (text, level) {
 }
 
 // highlight code
-renderer.code = function (code, lang) {
+renderer.code = function (code, lang = '') {
   const hl = Prism.highlight(code, Prism.languages[lang] || Prism.languages.markup)
 
   return `<pre data-lang="${lang}"><code class="lang-${lang}">${hl}</code></pre>`