diff --git a/.readthedocs.yml b/.readthedocs.yml
index 001a8b1cda..b0c36ed98b 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -5,6 +5,11 @@ build:
   tools:
     python: "mambaforge-4.10"
 
+  # Append fixed Python version to requirements
+  jobs:
+    pre_create_environment:
+      - echo "  - python=3.9" >> requirements/env_climada.yml
+
 conda:
   environment: requirements/env_climada.yml