diff --git a/setup.py b/setup.py
index 5678aaeb68..66b524fb3a 100644
--- a/setup.py
+++ b/setup.py
@@ -39,7 +39,7 @@ def get_version(module, path):
 )
 
 INSTALL_REQUIRES = [
-    'cylc-sphinx-extensions>=1.3',
+    'cylc-sphinx-extensions>=1.3.1',
     'eralchemy==1.2.*',
     'hieroglyph>=2.1.0',
     'sphinx>=3.0.0',