diff --git a/doc/requirements.txt b/doc/requirements.txt
index 029d0f8..362f96b 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -1,6 +1,6 @@
 # Requirements for building the `shell-logger` documentation.
 
-sphinx
+sphinx<=9.0.0
 sphinx-argparse
 sphinx-autodoc-typehints
 sphinx-copybutton