diff --git a/SimPEG/PropMaps.py b/SimPEG/PropMaps.py
index 65b735b8..6ce61ccb 100644
--- a/SimPEG/PropMaps.py
+++ b/SimPEG/PropMaps.py
@@ -52,6 +52,8 @@ class Property(object):
             if mapping is None and prop.propertyLink is not None:
                 linkName, linkMapClass = prop.propertyLink
                 linkMap = linkMapClass(None)
+                if getattr(self, '%sMap'%linkName, None) is None:
+                    return prop.defaultVal
                 m = getattr(self, '%s'%linkName)
                 return linkMap * m
 
diff --git a/SimPEG/Tests/test_PropMaps.py b/SimPEG/Tests/test_PropMaps.py
index 75c747cf..c2726d71 100644
--- a/SimPEG/Tests/test_PropMaps.py
+++ b/SimPEG/Tests/test_PropMaps.py
@@ -103,6 +103,8 @@ class TestPropMaps(unittest.TestCase):
         assert pm.sigmaDeriv is not None
         assert pm.rhoDeriv is not None
 
+        assert pm.mu == mu_0
+        assert pm.mui == 1.0/mu_0
         assert pm.muMap is None
         assert pm.muDeriv is None
         assert pm.muiMap is None