diff --git a/klamath/elements.py b/klamath/elements.py
index 8c77162..302921c 100644
--- a/klamath/elements.py
+++ b/klamath/elements.py
@@ -3,7 +3,6 @@ Functionality for reading/writing elements (geometry, text labels,
  structure references) and associated properties.
 """
 from typing import IO, TypeVar
-from collections.abc import Mapping
 from abc import ABCMeta, abstractmethod
 from dataclasses import dataclass
 
@@ -57,7 +56,7 @@ def read_properties(stream: IO[bytes]) -> dict[int, bytes]:
     return properties
 
 
-def write_properties(stream: IO[bytes], properties: Mapping[int, bytes]) -> int:
+def write_properties(stream: IO[bytes], properties: dict[int, bytes]) -> int:
     """
     Write element properties.
 
@@ -148,7 +147,7 @@ class Reference(Element):
     colrow: tuple[int, int] | NDArray[numpy.int16] | None
     """ Number of columns and rows (AREF) or None (SREF) """
 
-    properties: Mapping[int, bytes]
+    properties: dict[int, bytes]
     """ Properties associated with this reference. """
 
     @classmethod
@@ -230,7 +229,7 @@ class Boundary(Element):
     xy: NDArray[numpy.int32]
     """ Ordered vertices of the shape. First and last points should be identical. """
 
-    properties: Mapping[int, bytes]
+    properties: dict[int, bytes]
     """ Properties for the element. """
 
     @classmethod
@@ -276,7 +275,7 @@ class Path(Element):
     xy: NDArray[numpy.int32]
     """ Path centerline coordinates """
 
-    properties: Mapping[int, bytes]
+    properties: dict[int, bytes]
     """ Properties for the element. """
 
     @classmethod
@@ -341,7 +340,7 @@ class Box(Element):
     xy: NDArray[numpy.int32]
     """ Box coordinates (5 pairs) """
 
-    properties: Mapping[int, bytes]
+    properties: dict[int, bytes]
     """ Properties for the element. """
 
     @classmethod
@@ -375,7 +374,7 @@ class Node(Element):
     xy: NDArray[numpy.int32]
     """ 1-50 pairs of coordinates. """
 
-    properties: Mapping[int, bytes]
+    properties: dict[int, bytes]
     """ Properties for the element. """
 
     @classmethod
@@ -435,7 +434,7 @@ class Text(Element):
     string: bytes
     """ Text content """
 
-    properties: Mapping[int, bytes]
+    properties: dict[int, bytes]
     """ Properties for the element. """
 
     @classmethod
diff --git a/klamath/test_basic.py b/klamath/test_basic.py
index 287f7a9..4d686d9 100644
--- a/klamath/test_basic.py
+++ b/klamath/test_basic.py
@@ -120,7 +120,7 @@ def test_pack_ascii() -> None:
     assert pack_ascii(b'321') == b'321\0'
 
 
-def test_invalid_date() -> None:
+def test_invalid_date():
     default = [datetime(1900, 1, 1, 0, 0, 0)]
     assert parse_datetime(pack_int2((0, 0, 0, 0, 0, 0))) == default
     assert parse_datetime(pack_int2((0, 1, 32, 0, 0, 0))) == default