diff --git a/docs/requirements-docs.txt b/docs/requirements-docs.txt
index ebfd603..e2da1b4 100644
--- a/docs/requirements-docs.txt
+++ b/docs/requirements-docs.txt
@@ -1,5 +1,5 @@
 # Requirements to build hpcss' documentation.
 
-sphinx >=5.0, <10.0
+sphinx >=9.1.0, <10.0
 sphinx-rtd-theme >=3.0, <4.0
 tomlkit >=0.1, < 1.0