diff --git a/Docs/sphinx_doc/conf.py b/Docs/sphinx_doc/conf.py
index bc27bbfa8..77f4b4211 100644
--- a/Docs/sphinx_doc/conf.py
+++ b/Docs/sphinx_doc/conf.py
@@ -30,7 +30,10 @@
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
-extensions = [ 'sphinx.ext.mathjax']
+extensions = [
+    'sphinx.ext.mathjax',
+    'sphinx_rtd_theme',
+]
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']