diff --git a/.readthedocs.yaml b/.readthedocs.yaml
index 18f92a04..1d322ce3 100644
--- a/.readthedocs.yaml
+++ b/.readthedocs.yaml
@@ -12,7 +12,7 @@ sphinx:
 formats: []
 
 python:
-  version: "3.10"
+  version: "3.9"
   install:
     - requirements: docs/requirements.txt
     - method: pip
diff --git a/noxfile.py b/noxfile.py
index 3b16b5b3..9437d0ef 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -233,7 +233,7 @@ def functional(session):
     session.run(*run_args, env=env)
 
 
-@nox.session(py=DEFAULT_INTERPRETER)
+@nox.session(py="3.9")
 def docs(session):
     # Install all dependencies.
     session.install(*DOCS_DEPS)