diff --git a/galsec.py b/galsec.py
index 37b683b..d483b51 100644
--- a/galsec.py
+++ b/galsec.py
@@ -417,7 +417,7 @@ class Galsec:
              spacing between two y bins
         """
 
-        self.cartesian_binning(delta_x, delta_y)
+        self.cartesian_binning(delta_x, delta_y, delta_z)
         self.grouped_data = {}
         self.sectors = {}