diff --git a/audformat/core/column.py b/audformat/core/column.py
index d4d90574..7cfc0f2f 100644
--- a/audformat/core/column.py
+++ b/audformat/core/column.py
@@ -1,4 +1,4 @@
-from __future__ import annotations  # allow typing without string
+from __future__ import annotations
 
 import typing
 import warnings
diff --git a/audformat/core/typing.py b/audformat/core/typing.py
index 08217e25..ab1c00e2 100644
--- a/audformat/core/typing.py
+++ b/audformat/core/typing.py
@@ -1,32 +1,27 @@
 from __future__ import annotations
 
-import typing
+from collections.abc import Sequence
 
 import numpy as np
 import pandas as pd
 
 
-Files = typing.Union[
-    str,
-    typing.Sequence[str],
-    pd.Index,
-    pd.Series,
-]
-Timestamps = typing.Union[
-    float,
-    int,
-    str,
-    pd.Timedelta,
-    typing.Sequence[typing.Union[float, int, str, pd.Timedelta]],
-    pd.Index,
-    pd.Series,
-]
-Values = typing.Union[
-    int,
-    float,
-    str,
-    pd.Timedelta,
-    typing.Sequence[typing.Union[int, float, str, pd.Timedelta],],
-    np.ndarray,
-    pd.Series,
-]
+Files = str | Sequence[str] | pd.Index | pd.Series
+Timestamps = (
+    float
+    | int
+    | str
+    | pd.Timedelta
+    | Sequence[float | int | str | pd.Timedelta]
+    | pd.Index
+    | pd.Series
+)
+Values = (
+    int
+    | float
+    | str
+    | pd.Timedelta
+    | Sequence[int | float | str | pd.Timedelta]
+    | np.ndarray
+    | pd.Series
+)