diff --git a/tiatoolbox/utils/misc.py b/tiatoolbox/utils/misc.py
index 6c755d04e..6db19e23c 100644
--- a/tiatoolbox/utils/misc.py
+++ b/tiatoolbox/utils/misc.py
@@ -8,7 +8,7 @@
 import tempfile
 import zipfile
 from pathlib import Path
-from typing import IO, TYPE_CHECKING
+from typing import IO, TYPE_CHECKING, cast
 
 import cv2
 import joblib
@@ -1304,7 +1304,7 @@ def process_contours(
 
 
 def dict_to_store_semantic_segmentor(
-    patch_output: dict | zarr.group,
+    patch_output: dict | zarr.Group,
     scale_factor: tuple[float, float],
     class_dict: dict | None = None,
     save_path: Path | None = None,
@@ -1352,6 +1352,7 @@ def dict_to_store_semantic_segmentor(
             cv2.RETR_CCOMP,
             cv2.CHAIN_APPROX_NONE,
         )
+        contours = cast("list[np.ndarray]", contours)
 
         annotations_list_ = process_contours(contours, hierarchy, scale_factor)
         annotations_list.extend(annotations_list_)