diff -Nur a/setup.py b/setup.py
--- a/setup.py	2019-12-08 18:21:18.000000000 +0800
+++ b/setup.py	2022-08-16 11:39:11.119234654 +0800
@@ -2,7 +2,7 @@
 
 from setuptools import setup, find_packages
 
-requires = ['blockdiag>=1.5.0', 'Sphinx>=2.0']
+requires = ['blockdiag>=1.5.0', 'Sphinx>=1.8']
 
 setup(
     name='sphinxcontrib-blockdiag',