diff --git a/.github/workflows/tests-ubuntu.yml b/.github/workflows/tests-ubuntu.yml
index 83339f6c..95181dcd 100644
--- a/.github/workflows/tests-ubuntu.yml
+++ b/.github/workflows/tests-ubuntu.yml
@@ -48,7 +48,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ['3.13']
+        python-version: ['3.12']  # keep in sync with .readthedocs.yml
         tox-job: ["mypy", "docs", "linters", "types", "twinecheck"]
 
     steps:
diff --git a/.readthedocs.yml b/.readthedocs.yml
index de4de283..ae2ee300 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -6,7 +6,7 @@ sphinx:
 build:
   os: ubuntu-22.04
   tools:
-    python: "3.13"  # Keep in sync with .github/workflows/tests-ubuntu.yml
+    python: "3.12"  # Keep in sync with .github/workflows/tests-ubuntu.yml
 
 python:
   install: