diff --git a/src/dinglehopper/align.py b/src/dinglehopper/align.py
index 1f7957a..cffdf98 100644
--- a/src/dinglehopper/align.py
+++ b/src/dinglehopper/align.py
@@ -1,6 +1,7 @@
 import math
 import unicodedata
 from math import ceil
+from typing import Union
 
 from rapidfuzz.distance import Levenshtein
 
@@ -14,7 +15,7 @@ def align(t1, t2):
     return seq_align(s1, s2)
 
 
-def score_hint(er: float, n: int) -> int | None:
+def score_hint(er: float, n: int) -> Union[int, None]:
     """Calculate RapidFuzz score hint for a given error rate and count.
 
     Gives the score hint for the distance functions (= expected distance) or None if
diff --git a/src/dinglehopper/character_error_rate.py b/src/dinglehopper/character_error_rate.py
index 3b8c0cc..5e2e02c 100644
--- a/src/dinglehopper/character_error_rate.py
+++ b/src/dinglehopper/character_error_rate.py
@@ -1,5 +1,5 @@
 import unicodedata
-from typing import Tuple
+from typing import List, Tuple
 
 from multimethod import multimethod
 from uniseg.graphemecluster import grapheme_clusters
@@ -10,7 +10,7 @@ from .extracted_text import ExtractedText
 
 @multimethod
 def character_error_rate_n(
-    reference: list[str], compared: list[str]
+    reference: List[str], compared: List[str]
 ) -> Tuple[float, int]:
     """
     Compute character error rate.
diff --git a/src/dinglehopper/edit_distance.py b/src/dinglehopper/edit_distance.py
index ef90d81..9f7d309 100644
--- a/src/dinglehopper/edit_distance.py
+++ b/src/dinglehopper/edit_distance.py
@@ -2,13 +2,14 @@ import unicodedata
 
 from multimethod import multimethod
 from rapidfuzz.distance import Levenshtein
+from typing import List
 from uniseg.graphemecluster import grapheme_clusters
 
 from .extracted_text import ExtractedText
 
 
 @multimethod
-def distance(seq1: list[str], seq2: list[str]):
+def distance(seq1: List[str], seq2: List[str]):
     """Compute the Levenshtein edit distance between two lists of grapheme clusters.
 
     This assumes that the grapheme clusters are already normalized.
diff --git a/src/dinglehopper/extracted_text.py b/src/dinglehopper/extracted_text.py
index 28678e4..49882b7 100644
--- a/src/dinglehopper/extracted_text.py
+++ b/src/dinglehopper/extracted_text.py
@@ -4,7 +4,7 @@ import re
 import unicodedata
 from contextlib import suppress
 from itertools import repeat
-from typing import Optional
+from typing import Optional, List
 
 import attr
 import numpy as np
@@ -135,7 +135,7 @@ class ExtractedText:
     segments = attr.ib(type=Optional[list], converter=attr.converters.optional(list))
     joiner = attr.ib(type=Optional[str])
     _text = attr.ib(type=Optional[str])
-    _grapheme_clusters = attr.ib(type=Optional[list[str]])
+    _grapheme_clusters = attr.ib(type=Optional[List[str]])
 
     @segments.validator
     def check(self, _, value):