diff --git a/docs/requirements.txt b/docs/requirements.txt
index c0ca6cfd3..da707112c 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -4,5 +4,6 @@ gevent
 myst-parser[linkify]
 pydata_sphinx_theme
 pygments>=2.6
-sphinx>=3.0.4
+# enum-tools doesn't work with sphinx 9, yet
+sphinx==8.*
 tornado