diff --git a/{{cookiecutter.project_slug}}/.readthedocs.yml b/{{cookiecutter.project_slug}}/.readthedocs.yml
index 05bdd515..b4cf0c08 100644
--- a/{{cookiecutter.project_slug}}/.readthedocs.yml
+++ b/{{cookiecutter.project_slug}}/.readthedocs.yml
@@ -3,7 +3,10 @@ version: 2
 sphinx:
   configuration: docs/conf.py
 
-python:
+build:
   image: testing
+
+python:
+  version: 3.9
   install:
     - requirements: requirements/local.txt