diff --git a/docs/source/conf.py b/docs/source/conf.py
index fc5a076..5ad8dcf 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -35,5 +35,10 @@ html_theme = 'sphinx_rtd_theme'
 epub_show_urls = 'footnote'
 
 
-def setup(app):
-   app.add_css_file("docs/source/quartz.css")
+html_static_path = ['_static']
+
+# These paths are either relative to html_static_path
+# or fully qualified paths (eg. https://...)
+html_css_files = [
+    'css/custom.css',
+]