diff --git a/src/zolfa/nd2reader/parser.py b/src/zolfa/nd2reader/parser.py
index 45fcde16ef6ac2550f1c8e2f0ca77aa283aff5cf..60b2d141c82f53268c1037a69c39f110b5544e83 100644
--- a/src/zolfa/nd2reader/parser.py
+++ b/src/zolfa/nd2reader/parser.py
@@ -277,6 +277,7 @@ class Parser(object):
         """
         return {channel: n for n, channel in enumerate(self.metadata["channels"])}
 
+    # TODO: create missing test cases for slices
     def _get_raw_slice_data(self, xywh, image_group_number, channel, height, width):
         """Reads the raw bytes and the timestamp of a rectangular slice
         of an image.
@@ -322,7 +323,7 @@ class Parser(object):
         # Read ROI: row-by-row
         image_start_pos = chunk_location + 16 + relative_offset + 8
 
-        line_bytemask = np.zeros(size_c, dtype=np.bool)
+        line_bytemask = np.zeros(size_c, dtype=bool)
         line_bytemask[channel] = True
         line_bytemask = np.tile(line_bytemask.repeat(2),w)