diff --git a/.npmignore b/.npmignore
index 69292480..a4cf44f0 100644
--- a/.npmignore
+++ b/.npmignore
@@ -8,6 +8,7 @@ test
 .travis.yml
 appveyor.yml
 mkdocs.yml
+docs/css/
 vendor
 .prebuildrc
 .nyc_output
diff --git a/docs/css/extra.css b/docs/css/extra.css
new file mode 100644
index 00000000..e2bc8e06
--- /dev/null
+++ b/docs/css/extra.css
@@ -0,0 +1,5 @@
+/* Nest document subheadings in navigation */
+ul.subnav ul:not(.subnav) {
+  padding-left: 2em;
+  font-size: 80%;
+}
diff --git a/mkdocs.yml b/mkdocs.yml
index 21aaa06a..5a1f7688 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -5,6 +5,8 @@ site_description: High performance Node.js image processing, the fastest module
 copyright: <a href="https://pixelplumbing.com/">pixelplumbing.com</a>
 google_analytics: ['UA-13034748-12', 'sharp.pixelplumbing.com']
 theme: readthedocs
+extra_css:
+  - css/extra.css
 markdown_extensions:
   - toc:
       permalink: True