diff --git a/SimPEG/Survey.py b/SimPEG/Survey.py
index f2637e95..0d56145f 100644
--- a/SimPEG/Survey.py
+++ b/SimPEG/Survey.py
@@ -353,7 +353,10 @@ class Fields(object):
         else:
             # Aliased fields
             alias, loc, func = self.aliasFields[name]
-            out = func(self, self._fields[alias][:,ind], ind)
+            if type(func) is str:
+                assert hasattr(self, func), 'The alias field function is a string, but it does not exist in the Fields class.'
+                func = getattr(self, func)
+            out = func(self._fields[alias][:,ind], ind)
 
         if out.shape[1] == 1:
             out = Utils.mkvc(out)
@@ -431,16 +434,19 @@ class TimeFields(Fields):
         else:
             # Aliased fields
             alias, loc, func = self.aliasFields[name]
+            if type(func) is str:
+                assert hasattr(self, func), 'The alias field function is a string, but it does not exist in the Fields class.'
+                func = getattr(self, func)
             pointerFields = self._fields[alias][:,txInd,timeInd]
             pointerShape = self._correctShape(alias, ind, deflate=True)
             pointerFields = pointerFields.reshape(pointerShape, order='F')
             if len(pointerShape) < 3:
-                out = func(self, pointerFields, txInd)
+                out = func(pointerFields, txInd)
             else: #loop over the time steps
                 nT = pointerShape[2]
                 out = range(nT)
                 for i in range(nT):
-                    out[i] = func(self, pointerFields[:,:,i], txInd)
+                    out[i] = func(pointerFields[:,:,i], txInd)
                     out[i] = out[i][:,:,np.newaxis]
                 out = np.concatenate(out, axis=2)
 
diff --git a/SimPEG/Tests/test_Survey.py b/SimPEG/Tests/test_Survey.py
index 53a252be..df476ebb 100644
--- a/SimPEG/Tests/test_Survey.py
+++ b/SimPEG/Tests/test_Survey.py
@@ -133,7 +133,7 @@ class FieldsTest_Alias(unittest.TestCase):
         txList = [Tx0,Tx1,Tx2,Tx3,Tx4]
         survey = Survey.BaseSurvey(txList=txList)
         self.D = Survey.Data(survey)
-        self.F = Survey.Fields(mesh, survey, knownFields={'e':'E'}, aliasFields={'b':['e','F',(lambda F, e, ind: F.mesh.edgeCurl * e)]})
+        self.F = Survey.Fields(mesh, survey, knownFields={'e':'E'}, aliasFields={'b':['e','F',(lambda e, ind: self.F.mesh.edgeCurl * e)]})
         self.Tx0 = Tx0
         self.Tx1 = Tx1
         self.mesh = mesh
@@ -287,8 +287,8 @@ class FieldsTest_Time_Aliased(unittest.TestCase):
         survey = Survey.BaseSurvey(txList=txList)
         prob = Problem.BaseTimeProblem(mesh, timeSteps=[(10.,3), (20.,2)])
         survey.pair(prob)
-        def alias(F, b, ind):
-            return F.mesh.edgeCurl.T * b
+        def alias(b, ind):
+            return self.F.mesh.edgeCurl.T * b
         self.F = Survey.TimeFields(mesh, survey, knownFields={'b':'F'}, aliasFields={'e':['b','E',alias]})
         self.Tx0 = Tx0
         self.Tx1 = Tx1