diff --git a/src/napatrackmater/Trackmate.py b/src/napatrackmater/Trackmate.py
index fb1789f8..dcc7d74e 100644
--- a/src/napatrackmater/Trackmate.py
+++ b/src/napatrackmater/Trackmate.py
@@ -2912,8 +2912,8 @@ def cell_angular_change(vec_cell):
     vec = np.asarray(vec_cell)
     vec = vec / np.linalg.norm(vec)
     num_dims = len(vec)
-    unit_vector = np.ones(num_dims)
-    unit_vector[-1] = 0
+    unit_vector = np.zeros(num_dims)
+    unit_vector[-1] = 1
     unit_vector = unit_vector / np.linalg.norm(unit_vector)
     theta = np.arccos(np.clip(np.dot(vec, unit_vector), -1.0, 1.0))
     angle = np.rad2deg(theta)
diff --git a/src/napatrackmater/_version.py b/src/napatrackmater/_version.py
index 20d0a1e9..09afeae9 100644
--- a/src/napatrackmater/_version.py
+++ b/src/napatrackmater/_version.py
@@ -1,2 +1,2 @@
-__version__ = version = "5.0.0"
-__version_tuple__ = version_tuple = (5, 0, 0)
+__version__ = version = "5.0.1"
+__version_tuple__ = version_tuple = (5, 0, 1)