diff --git a/pyproject.toml b/pyproject.toml
index acbed880..5f6a26dc 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -114,3 +114,18 @@ markers = [
     "setup_args : kwargs for setup fixture.",
     "slow: slow tests",
 ]
+
+[tool.mypy]
+allow_incomplete_defs = true  # FIXME
+allow_untyped_decorators = false
+allow_untyped_defs = true  # FIXME
+ignore_missing_imports = true
+no_implicit_optional = true
+show_error_codes = true
+warn_redundant_casts = true
+warn_unused_ignores = true
+warn_unreachable = true
+
+[[tool.mypy.overrides]]
+module = ["*.tests.*"]
+allow_untyped_defs = true
diff --git a/versioned_hdf5/api.py b/versioned_hdf5/api.py
index 521dd526..76f0a42e 100644
--- a/versioned_hdf5/api.py
+++ b/versioned_hdf5/api.py
@@ -152,6 +152,11 @@ def current_version(self):
         """
         return self._versions.attrs["current_version"]
 
+    @current_version.setter
+    def current_version(self, version_name):
+        set_current_version(self.f, version_name)
+        self._version_cache.clear()
+
     @property
     def data_version_identifier(self) -> str:
         """Return the data version identifier.
@@ -180,11 +185,6 @@ def data_version_identifier(self, version: int):
         """
         self.f["_version_data/versions"].attrs["data_version"] = version
 
-    @current_version.setter
-    def current_version(self, version_name):
-        set_current_version(self.f, version_name)
-        self._version_cache.clear()
-
     def get_version_by_name(self, version):
         if version.startswith("/"):
             raise ValueError(
diff --git a/versioned_hdf5/backend.py b/versioned_hdf5/backend.py
index dea853dc..878b9176 100644
--- a/versioned_hdf5/backend.py
+++ b/versioned_hdf5/backend.py
@@ -320,7 +320,7 @@ def _verify_new_chunk_reuse(
         assert_array_equal(to_be_reused, to_be_written)
     except AssertionError as e:
         raise ValueError(
-            f"Hash {data_hash} of existing data chunk {reused_chunk} "
+            f"Hash {data_hash!r} of existing data chunk {reused_chunk} "
             f"matches the hash of new data chunk {chunk_being_written}, "
             "but data does not."
         ) from e