diff --git a/mkdocs.yml b/mkdocs.yml
index 7cba17bd..2603f142 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -104,6 +104,7 @@ markdown_extensions:
   - footnotes
   - toc:
       permalink: true
+      toc_depth: 4
 
 extra_javascript:
   - javascripts/mathjax.js