diff --git a/.readthedocs.yaml b/.readthedocs.yaml
index 9608d3959..5cbae054f 100644
--- a/.readthedocs.yaml
+++ b/.readthedocs.yaml
@@ -15,7 +15,7 @@ formats:
 
 # Optionally set the version of Python and requirements required to build your docs
 python:
-   version: "3.9"
+   version: "3.6"
    install:
    - requirements: developer-docs/requirements.txt