diff --git a/SimPEG/Mesh/DiffOperators.py b/SimPEG/Mesh/DiffOperators.py
index 05c79b73..a7a7b0cb 100644
--- a/SimPEG/Mesh/DiffOperators.py
+++ b/SimPEG/Mesh/DiffOperators.py
@@ -407,7 +407,7 @@ class DiffOperators(object):
             if self.dim < 3: return None
             if getattr(self, '_cellGradz', None) is None:
                 BC = ['neumann', 'neumann']
-                n = self.n
+                n = self.vnC
                 G3 = kron3(ddxCellGrad(n[2], BC), speye(n[1]), speye(n[0]))
                 # Compute areas of cell faces & volumes
                 V = self.aveCC2F*self.vol