diff --git a/environment.yml b/environment.yml
index 911641d7..6010fda0 100644
--- a/environment.yml
+++ b/environment.yml
@@ -7,7 +7,7 @@ dependencies:
   - pip
   - pip:
     - jupyter-book==1.0.4post1
-    - quantecon-book-theme==0.20.0
+    - quantecon-book-theme==0.20.2
     - sphinx-tojupyter==0.6.0
     - sphinxext-rediraffe==0.3.0
     - sphinx-exercise==1.2.1
diff --git a/lectures/_config.yml b/lectures/_config.yml
index bb8173d0..552b2cf9 100644
--- a/lectures/_config.yml
+++ b/lectures/_config.yml
@@ -97,6 +97,14 @@ sphinx:
       repository_url: https://github.com/QuantEcon/lecture-python-intro
       nb_repository_url: https://github.com/QuantEcon/lecture-python-intro.notebooks
       path_to_docs: lectures
+      languages:
+        - code: en
+          name: English
+          url: https://intro.quantecon.org/
+        - code: zh-cn
+          name: 中文
+          url: https://quantecon.github.io/lecture-intro.zh-cn/
+      current_language: en
       twitter: quantecon
       twitter_logo_url: https://assets.quantecon.org/img/qe-twitter-logo.png
       og_logo_url: https://assets.quantecon.org/img/qe-og-logo.png