diff --git a/src/toolbox_scs/base/knife_edge.py b/src/toolbox_scs/base/knife_edge.py
index 26b8ae574558dea21859898e22aff2e7c8e86817..92d8b3a3e2f8a3bbdacc1bf9aa732aa22609041f 100644
--- a/src/toolbox_scs/base/knife_edge.py
+++ b/src/toolbox_scs/base/knife_edge.py
@@ -148,7 +148,7 @@ def arrays_to1d(arrX: np.ndarray, arrY: np.ndarray):
 def range_mask(array, minimum=None, maximum=None):
     """Retrieve the resulting array from the given minimum and maximum
     """
-    default = np.ones(array.shape, dtype=np.bool)
+    default = np.ones(array.shape, dtype=bool)
     min_slice, max_slice = default, default
     if minimum is not None:
         if minimum > np.nanmax(array):