diff --git a/lectures/_config.yml b/lectures/_config.yml
index 5da1c55b..9211779b 100644
--- a/lectures/_config.yml
+++ b/lectures/_config.yml
@@ -45,6 +45,8 @@ sphinx:
     nb_code_prompt_show: "Show {type}"
     suppress_warnings: [mystnb.unknown_mime_type]
     # -------------
+    html_js_files:
+      - https://cdnjs.cloudflare.com/ajax/libs/require.js/2.3.4/require.min.js
     html_favicon: _static/lectures-favicon.ico
     html_theme: quantecon_book_theme
     html_static_path: ['_static']