diff --git a/docs/conf.py b/docs/conf.py
index b0918be5..b11cd052 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -26,7 +26,7 @@ sys.path.insert(0, os.path.abspath('.'))
 
 # If your documentation needs a minimal Sphinx version, state it here.
 #
-# needs_sphinx = '1.0'
+needs_sphinx = '2.1'
 
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom