diff --git a/doc/requirements.txt b/doc/requirements.txt
index 1d030dd6a6..965e036659 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -2,7 +2,7 @@ ansible
 # NOTE(ianw) 2021-07-13: <4.1.0 until related issue in
 # sphixcontrib-httpdomain fixed
 #  https://github.com/sphinx-contrib/httpdomain/pull/51
-sphinx>=1.6.1,<4.1.0
+sphinx>=1.8,<4.1.0
 sphinxcontrib-blockdiag>=1.1.0
 sphinxcontrib-programoutput
 sphinx-autodoc-typehints