diff --git a/cv_analysis/utils/postprocessing.py b/cv_analysis/utils/postprocessing.py
index 040f4bb..2f40c48 100644
--- a/cv_analysis/utils/postprocessing.py
+++ b/cv_analysis/utils/postprocessing.py
@@ -9,7 +9,7 @@ def remove_overlapping(rectangles: Iterable[Rectangle]) -> List[Rectangle]:
     def overlap(a: Rectangle, rect2: Rectangle) -> float:
         return a.intersection(rect2) > 0
 
-    def does_not_overlap(rect: Rectangle, rectangles: Iterable[Rectangle]) -> list:
+    def does_not_overlap(rect: Rectangle, rectangles: Iterable[Rectangle]) -> bool:
         return not any(overlap(rect, rect2) for rect2 in rectangles if not rect == rect2)
 
     rectangles = list(filter(partial(does_not_overlap, rectangles=rectangles), rectangles))
@@ -25,7 +25,10 @@ def __remove_isolated_unsorted(rectangles: Iterable[Rectangle]) -> List[Rectangl
     def is_connected(rect: Rectangle, rectangles: Iterable[Rectangle]):
         return any(rect.adjacent(rect2) for rect2 in rectangles if not rect == rect2)
 
-    rectangles = list(filter(partial(is_connected, rectangles=list(rectangles)), rectangles))
+    if not isinstance(rectangles, list):
+        rectangles = list(rectangles)
+
+    rectangles = list(filter(partial(is_connected, rectangles=rectangles), rectangles))
     return rectangles