diff --git a/docs/mkdocs.yml b/docs/mkdocs.yml
index a6e159f15..2a5079ae4 100644
--- a/docs/mkdocs.yml
+++ b/docs/mkdocs.yml
@@ -20,6 +20,7 @@ theme:
     - content.action.edit
     - content.tooltips
     - header.autohide
+    - navigation.indexes
     - navigation.expand
     - navigation.footer
     - navigation.instant