diff --git a/cv_analysis/utils/postprocessing.py b/cv_analysis/utils/postprocessing.py
index ea4c4ee..472700f 100644
--- a/cv_analysis/utils/postprocessing.py
+++ b/cv_analysis/utils/postprocessing.py
@@ -1,11 +1,11 @@
 from collections import namedtuple
 from functools import partial
 from itertools import starmap, compress
-from typing import Iterable
+from typing import Iterable, List
 from cv_analysis.utils.structures import Rectangle
 
 
-def remove_overlapping(rectangles: Iterable[Rectangle]) -> list[Rectangle]:
+def remove_overlapping(rectangles: Iterable[Rectangle]) -> List[Rectangle]:
     def overlap(a: Rectangle, rect2: Rectangle) -> float:
         return a.intersection(rect2) > 0
 
@@ -16,12 +16,12 @@ def remove_overlapping(rectangles: Iterable[Rectangle]) -> list[Rectangle]:
     return rectangles
 
 
-def remove_included(rectangles: Iterable[Rectangle]) -> list[Rectangle]:
+def remove_included(rectangles: Iterable[Rectangle]) -> List[Rectangle]:
     keep = [rect for rect in rectangles if not rect.is_included(rectangles)]
     return keep
 
 
-def __remove_isolated_unsorted(rectangles: Iterable[Rectangle]) -> list[Rectangle]:
+def __remove_isolated_unsorted(rectangles: Iterable[Rectangle]) -> List[Rectangle]:
     def is_connected(rect: Rectangle, rectangles: Iterable[Rectangle]):
         return any(rect.adjacent(rect2) for rect2 in rectangles if not rect == rect2)
 
@@ -29,7 +29,7 @@ def __remove_isolated_unsorted(rectangles: Iterable[Rectangle]) -> list[Rectangl
     return rectangles
 
 
-def __remove_isolated_sorted(rectangles: Iterable[Rectangle]) -> list[Rectangle]:
+def __remove_isolated_sorted(rectangles: Iterable[Rectangle]) -> List[Rectangle]:
     def is_connected(left, center, right):
         return any([left.adjacent(center), center.adjacent(right)])
 
@@ -42,7 +42,7 @@ def __remove_isolated_sorted(rectangles: Iterable[Rectangle]) -> list[Rectangle]
     return rectangles
 
 
-def remove_isolated(rectangles: Iterable[Rectangle], input_unsorted=True) -> list[Rectangle]:
+def remove_isolated(rectangles: Iterable[Rectangle], input_unsorted=True) -> List[Rectangle]:
     return (__remove_isolated_unsorted if input_unsorted else __remove_isolated_sorted)(rectangles)