diff --git a/sphinx/requirements.txt b/sphinx/requirements.txt
index 7d2e88c43..c8aba8c96 100644
--- a/sphinx/requirements.txt
+++ b/sphinx/requirements.txt
@@ -11,6 +11,7 @@ cryptography>=3.0
 packaging
 pyyaml
 # needed for readthedocs builds:
+sphinx==6.2.1
 GitPython
 myst_parser
 sphinx_rtd_theme