diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 0064d032..d2c0fc91 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -40,7 +40,7 @@ repos:
         name: Check Python types
         priority: 0
         # Pillow is ignored in dependabot.yml
-        additional_dependencies: [flask, openslide-bin, pillow >= 12.1.0, types-PyYAML, types-setuptools]
+        additional_dependencies: [flask, openslide-bin, pillow >= 13.0.0, types-PyYAML, types-setuptools]
 
   - repo: https://github.com/rstcheck/rstcheck
     rev: v6.3.0
diff --git a/openslide/__init__.py b/openslide/__init__.py
index f3b4844d..f8c6e367 100644
--- a/openslide/__init__.py
+++ b/openslide/__init__.py
@@ -392,7 +392,8 @@ 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:
-                return img.format
+                # mypy will think img is Any until we drop Python 3.10
+                return img.format  # type: ignore[no-any-return]
         except OSError:
             return None