diff --git a/.github/maintainer/mkmaintainer.py b/.github/maintainer/mkmaintainer.py
index f399f13..0fba403 100755
--- a/.github/maintainer/mkmaintainer.py
+++ b/.github/maintainer/mkmaintainer.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 
 from __future__ import annotations
 
diff --git a/.github/workflows/python.yml b/.github/workflows/python.yml
index 8617fc3..db31092 100644
--- a/.github/workflows/python.yml
+++ b/.github/workflows/python.yml
@@ -16,7 +16,7 @@ env:
 jobs:
   pre-commit:
     name: Rerun pre-commit checks
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-slim
     outputs:
       dist-base: ${{ steps.paths.outputs.dist }}
       docs-base: ${{ steps.paths.outputs.docs }}
@@ -252,7 +252,7 @@ jobs:
   docs:
     name: Docs
     needs: pre-commit
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-slim
     steps:
     - name: Check out repo
       uses: actions/checkout@v5
@@ -279,7 +279,7 @@ jobs:
       name: pypi
       url: https://pypi.org/p/openslide-python
     needs: [pre-commit, tests, windows]
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-slim
     concurrency: release-${{ github.ref }}
     permissions:
       contents: write
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index a5d6c68..cc1b8a8 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -58,7 +58,7 @@ repos:
     hooks:
       - id: mypy
         name: Check Python types
-        additional_dependencies: [flask, openslide-bin, pillow, types-PyYAML, types-setuptools]
+        additional_dependencies: [flask, openslide-bin, pillow >= 12.1.0, types-PyYAML, types-setuptools]
 
   - repo: https://github.com/rstcheck/rstcheck
     rev: v6.2.5
diff --git a/openslide/__init__.py b/openslide/__init__.py
index 09bc03d..9332d24 100644
--- a/openslide/__init__.py
+++ b/openslide/__init__.py
@@ -394,9 +394,7 @@ def detect_format(cls, filename: lowlevel.Filename) -> str | None:
         If the file format is not recognized, return None."""
         try:
             with Image.open(filename) as img:
-                # img currently resolves as Any
-                # https://github.com/python-pillow/Pillow/pull/8362
-                return img.format  # type: ignore[no-any-return]
+                return img.format
         except OSError:
             return None