diff --git a/docs/source/conf.py b/docs/source/conf.py
index 8bb8d4fa9..91bebcc78 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -47,7 +47,7 @@
 
 
 def setup(app):
-    app.add_stylesheet("custom.css")  # may also be a URL
+    app.add_css_file("custom.css")  # may also be a URL
     app.add_config_value(
         "recommonmark_config", {"auto_toc_tree_section": "Contents"}, True
     )