diff --git a/CHANGES.rst b/CHANGES.rst
index ed3fd98..74df521 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -6,6 +6,7 @@ v0.3.3
 Released August 17, 2020
 
 * Make FPN seed optional in ``detector.dark_current``
+* Update ``np.ediff1d`` usage to be compatible with Numpy 1.19
 
 v0.3.2
 ------
diff --git a/lentil/detector.py b/lentil/detector.py
index ca1395c..77ccd4a 100644
--- a/lentil/detector.py
+++ b/lentil/detector.py
@@ -829,7 +829,7 @@ def _process_cube_intersections(inter, xyz, dxdydz):
     _dxdydz = dxdydz[inter['indx'], :].astype(np.float32)
 
     draylength = np.ediff1d(inter['raylength'], to_begin=(0.0,))
-    np.putmask(draylength, np.ediff1d(inter['indx'], to_begin=(1,)) != 0,
+    np.putmask(draylength, np.ediff1d(inter['indx'], to_begin=np.array([1], dtype=np.uint64)) != 0,
                inter['raylength'])
 
     inter_point = _xyz + inter['raylength'][:, None] * _dxdydz