diff --git a/bind/G4Calo.py b/bind/G4Calo.py
index d978d44..2959f39 100644
--- a/bind/G4Calo.py
+++ b/bind/G4Calo.py
@@ -82,7 +82,6 @@ class __G4System(_G4System):
                     **ijk_cube,
                     **material_dict[layer_material]
                 ))
-            z0 += layer_z
 
 
             #
@@ -113,7 +112,8 @@ class __G4System(_G4System):
                         showlegend=False,
                     )) 
                     
-                z0 += z
+    
+            z0 += layer_z