diff --git a/reference/book.toml b/reference/book.toml
index d8127cea..33676748 100644
--- a/reference/book.toml
+++ b/reference/book.toml
@@ -12,6 +12,7 @@ extra-watch-dirs = ["../packages"] # rebuild on Move Source changes
 
 [output.html]
 additional-css = ["theme/css/custom.css"]
+additional-js = ["theme/switcher.js"]
 git-repository-url = "https://github.com/MystenLabs/move-book"
 git-repository-icon = "fa-github"
 edit-url-template = "https://github.com/move-language/move/edit/main/language/documentation/book/{path}"