diff --git a/conf.py b/conf.py
index aa8b47d..8d82760 100644
--- a/conf.py
+++ b/conf.py
@@ -43,6 +43,7 @@ extensions = [
     'sphinx.ext.autodoc',
     'sphinx.ext.autosectionlabel',
     'sphinx.ext.todo',
+    'sphinx_rtd_theme',
 ]
 
 # Add any paths that contain templates here, relative to this directory.