diff --git a/SimPEG/Regularization.py b/SimPEG/Regularization.py
index 0a6f2622..d6780c45 100644
--- a/SimPEG/Regularization.py
+++ b/SimPEG/Regularization.py
@@ -55,7 +55,7 @@ class BaseRegularization(object):
     @property
     def W(self):
         """Full regularization weighting matrix W."""
-        return self._Pac.T * sp.identity(self.mesh.nC) * self. # or do we want sp.identity(self.mesh.nC) or even just Utils.Identity() ?
+        return self._Pac.T * sp.identity(self.mesh.nC) * self._Pac # or do we want sp.identity(self.mesh.nC) or even just Utils.Identity() ?
 
     @property
     def _Pac(self):