diff --git a/docs/source/conf.py b/docs/source/conf.py
index 00fab6a7ab..83570574dd 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -155,7 +155,7 @@ html_title = "OpenMC Documentation"
 html_static_path = ['_static']
 
 def setup(app):
-    app.add_stylesheet('theme_overrides.css')
+    app.add_css_file('theme_overrides.css')
 
 # If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
 # using the given strftime format.