diff --git a/SimPEG/Mesh/InnerProducts.py b/SimPEG/Mesh/InnerProducts.py
index 11f5d496..f8bcee46 100644
--- a/SimPEG/Mesh/InnerProducts.py
+++ b/SimPEG/Mesh/InnerProducts.py
@@ -109,9 +109,9 @@ class InnerProducts(object):
         return [V*proj(*locs[node][d-1]) for node in nodes]
 
 
-    def getFaceInnerProductDeriv(self, tensorType, doFast=True):
+    def getFaceInnerProductDeriv(self, prop, doFast=True):
         """
-            :param TensorType tensorType: type of the tensor: TensorType(mesh, sigma)
+            :param numpy.array prop: material property (tensor properties are possible) at each cell center (nC, (1, 3, or 6))
             :param bool doFast: do a faster implementation if available.
             :rtype: function
             :return: dMdmu(u), the derivative of the inner product matrix (u)
@@ -122,27 +122,27 @@ class InnerProducts(object):
             :rtype: scipy.csr_matrix
             :return: dMdmu, the derivative of the inner product matrix for a certain u
         """
-        return self._getInnerProductDeriv(tensorType, 'F', doFast=doFast)
+        return self._getInnerProductDeriv(prop, 'F', doFast=doFast)
 
 
-    def getEdgeInnerProductDeriv(self, tensorType, doFast=True):
+    def getEdgeInnerProductDeriv(self, prop, doFast=True):
         """
-            :param TensorType tensorType: type of the tensor: TensorType(mesh, sigma)
+            :param numpy.array prop: material property (tensor properties are possible) at each cell center (nC, (1, 3, or 6))
             :param bool doFast: do a faster implementation if available.
             :rtype: scipy.csr_matrix
             :return: dMdm, the derivative of the inner product matrix (nE, nC*nA)
         """
-        return self._getInnerProductDeriv(tensorType, 'E', doFast=doFast)
+        return self._getInnerProductDeriv(prop, 'E', doFast=doFast)
 
-    def _getInnerProductDeriv(self, tensorType, projType, doFast=True):
+    def _getInnerProductDeriv(self, prop, projType, doFast=True):
         """
-            :param TensorType tensorType: type of the tensor: TensorType(mesh, sigma)
+            :param numpy.array prop: material property (tensor properties are possible) at each cell center (nC, (1, 3, or 6))
             :param str projType: 'F' for faces 'E' for edges
             :param bool doFast: do a faster implementation if available.
             :rtype: scipy.csr_matrix
             :return: dMdm, the derivative of the inner product matrix (nE, nC*nA)
         """
-        assert isinstance(tensorType, TensorType), 'tensorType must be an instance of TensorType.'
+        tensorType = TensorType(self, prop)
         fast = None
 
         if hasattr(self, '_fastInnerProductDeriv') and doFast:
diff --git a/SimPEG/Tests/test_massMatricesDerivs.py b/SimPEG/Tests/test_massMatricesDerivs.py
index dd208c68..21ac8c41 100644
--- a/SimPEG/Tests/test_massMatricesDerivs.py
+++ b/SimPEG/Tests/test_massMatricesDerivs.py
@@ -16,7 +16,7 @@ class TestInnerProductsDerivs(unittest.TestCase):
             mesh = Mesh.TensorMesh(h)
         v = np.random.rand(mesh.nF)
         sig = np.random.rand(1) if rep is 0 else np.random.rand(mesh.nC*rep)
-        Md = mesh.getFaceInnerProductDeriv(Utils.TensorType(mesh, sig), doFast=fast)
+        Md = mesh.getFaceInnerProductDeriv(sig, doFast=fast)
         def fun(sig):
             M = mesh.getFaceInnerProduct(sig)
             return M*v, Md(v)
@@ -33,7 +33,7 @@ class TestInnerProductsDerivs(unittest.TestCase):
             mesh = Mesh.TensorMesh(h)
         v = np.random.rand(mesh.nE)
         sig = np.random.rand(1) if rep is 0 else np.random.rand(mesh.nC*rep)
-        Md = mesh.getEdgeInnerProductDeriv(Utils.TensorType(mesh, sig), doFast=fast)
+        Md = mesh.getEdgeInnerProductDeriv(sig, doFast=fast)
         def fun(sig):
             M = mesh.getEdgeInnerProduct(sig)
             return M*v, Md(v)