diff --git a/docs/conf.py b/docs/conf.py
index 488e82da7..0023a12b1 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -28,7 +28,8 @@ import sys, os
 extensions = [
   'sphinx.ext.todo', 
   'sphinx_copybutton',
-  'sphinx_tabs.tabs'
+  'sphinx_tabs.tabs',
+  'sphinx_rtd_theme'
 ]
 
 # Add any paths that contain templates here, relative to this directory.