diff --git a/book/_config.yml b/book/_config.yml
index 6ad58d4..d488258 100644
--- a/book/_config.yml
+++ b/book/_config.yml
@@ -43,6 +43,7 @@ sphinx:
     - download_link_replacer
     - sphinx.ext.extlinks
     - sphinx_image_inverter
+    - sphinx_iframes
     - sphinx_exercise
     - teachbooks_sphinx_tippy