diff --git a/.readthedocs.yaml b/.readthedocs.yaml
index baa2936..3d0da91 100644
--- a/.readthedocs.yaml
+++ b/.readthedocs.yaml
@@ -4,7 +4,7 @@ version: 2
 build:
   os: 'ubuntu-20.04'
   tools:
-    python: '3.10'
+    python: '3.9'
 
 mkdocs:
   configuration: mkdocs.yml