diff --git a/lib/core/Remarkable.js b/lib/core/Remarkable.js
index 92a8a950e0..710021a417 100644
--- a/lib/core/Remarkable.js
+++ b/lib/core/Remarkable.js
@@ -42,21 +42,24 @@ class Remarkable extends React.Component {
 
   renderMarkdown(source) {
     if (!this.md) {
+      const siteConfig = require(CWD + "/siteConfig.js");
+
       this.md = new Markdown({
         // Highlight.js expects hljs css classes on the code element.
         // This results in <pre><code class="hljs css javascript">
         langPrefix: 'hljs css ',
         highlight: function (str, lang) {
+          lang = lang || (siteConfig.highlight && siteConfig.highlight.defaultLang);
           if (lang && hljs.getLanguage(lang)) {
             try {
               return hljs.highlight(lang, str).value;
             } catch (err) {}
           }
-      
+
           try {
             return hljs.highlightAuto(str).value;
           } catch (err) {}
-      
+
           return '';
         }
       });
@@ -65,7 +68,6 @@ class Remarkable extends React.Component {
       this.md.use(anchors);
 
       // Allow client sites to register their own plugins
-      const siteConfig = require(CWD + "/siteConfig.js");
       if (siteConfig.markdownPlugins) {
         siteConfig.markdownPlugins.forEach(function(plugin) {
           this.md.use(plugin);
@@ -96,4 +98,4 @@ Remarkable.defaultProps = {
   options: {},
 };
 
-module.exports = Remarkable;
\ No newline at end of file
+module.exports = Remarkable;