diff --git a/pint_pandas/pint_array.py b/pint_pandas/pint_array.py
index 92906d1..b10372c 100644
--- a/pint_pandas/pint_array.py
+++ b/pint_pandas/pint_array.py
@@ -2,7 +2,7 @@
 import re
 import warnings
 from importlib.metadata import version
-from typing import Any, Callable, Dict, Optional, cast
+from typing import Any, Callable, Dict, Optional, Union, cast
 
 import numpy as np
 import pandas as pd
@@ -622,7 +622,7 @@ def unique(self):
         data = self._data
         return self._from_sequence(unique(data), dtype=self.dtype)
 
-    def __contains__(self, item) -> bool | np.bool_:
+    def __contains__(self, item) -> Union[bool, np.bool_]:
         if not isinstance(item, _Quantity):
             return False
         elif pd.isna(item.magnitude):