diff --git a/.binder/runtime.txt b/.binder/runtime.txt
index d2aca3a..8fdd907 100644
--- a/.binder/runtime.txt
+++ b/.binder/runtime.txt
@@ -1 +1 @@
-python-3.12
+python-3.9
diff --git a/.github/workflows/notebook.yml b/.github/workflows/notebook.yml
index c030fa7..f36a446 100644
--- a/.github/workflows/notebook.yml
+++ b/.github/workflows/notebook.yml
@@ -23,7 +23,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.10"
+          python-version: "3.9"
       - uses: astral-sh/setup-uv@v3
         with:
           enable-cache: true
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 7ddcba3..1e5ee58 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -13,6 +13,7 @@ repos:
     hooks:
       - id: check-dev-files
         args:
+          - --dev-python-version=3.9
           - --no-cd
           - --no-cspell-update
           - --no-github-actions
diff --git a/.python-version b/.python-version
index e4fba21..bd28b9c 100644
--- a/.python-version
+++ b/.python-version
@@ -1 +1 @@
-3.12
+3.9