diff --git a/SimPEG/Tests/test_Fields.py b/SimPEG/Tests/test_Fields.py
index 22189a15..bd75d712 100644
--- a/SimPEG/Tests/test_Fields.py
+++ b/SimPEG/Tests/test_Fields.py
@@ -147,7 +147,7 @@ class FieldsTest_Alias(unittest.TestCase):
 
     def test_aliasFunction(self):
         def alias(e, ind):
-            self.assertTrue(ind is self.Src0)
+            self.assertTrue(ind[0] is self.Src0)
             return self.F.mesh.edgeCurl * e
         F = Problem.Fields(self.F.mesh, self.F.survey, knownFields={'e':'E'}, aliasFields={'b':['e','F',alias]})
         e = np.random.rand(F.mesh.nE,1)