diff --git a/requirements-dev.txt b/requirements-dev.txt
index 2107597..3a9eb69 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -10,5 +10,5 @@ wheel
 docutils == 0.21.*
 furo
 myst-parser == 4.*
-sphinx == 8.*
+sphinx == 9.*
 sphinx-autodoc-typehints == 3.*
diff --git a/requirements-readthedocs.txt b/requirements-readthedocs.txt
index f24bee6..ba5bc07 100644
--- a/requirements-readthedocs.txt
+++ b/requirements-readthedocs.txt
@@ -6,5 +6,5 @@ pyjson5 == 2.0.0
 docutils == 0.21.*
 furo
 myst-parser == 4.*
-sphinx == 8.*
+sphinx == 9.*
 sphinx-autodoc-typehints == 3.*