diff --git a/composer/schema/field.py b/composer/schema/field.py
index d3268bf..554fdba 100644
--- a/composer/schema/field.py
+++ b/composer/schema/field.py
@@ -154,7 +154,7 @@ class FieldInstance(object):
         #return toStr(value)
 
     def display(self, value):
-        return value
+        return value or u''
         #return toStr(value)
 
     def unmarshall(self, value):
diff --git a/composer/schema/instance.py b/composer/schema/instance.py
index f96a636..2d9e967 100644
--- a/composer/schema/instance.py
+++ b/composer/schema/instance.py
@@ -55,7 +55,10 @@ class Instance(BaseInstance):
                 fi = f.getFieldInstance(self)
                 name = f.name
                 value = getattr(self.context, name) or fi.default
-                value = (mode == 'view' and fi.display(value)) or fi.marshall(value)
+                if mode == 'view':
+                    value = fi.display(value)
+                else:
+                    value = fi.marshall(value)
                 result[name] = value
         return result
 
diff --git a/media/tests.py b/media/tests.py
index acf1c02..de9cebd 100644
--- a/media/tests.py
+++ b/media/tests.py
@@ -18,10 +18,12 @@ dataDir = os.path.join(os.path.dirname(media.__file__), 'testdata')
 def clearDataDir():
     for fn in os.listdir(dataDir):
         path = os.path.join(dataDir, fn)
-        if os.path.isdir(path):
-            for subfn in os.listdir(path):
-                os.unlink(os.path.join(path, subfn))
-            os.rmdir(path)
+        if not fn.startswith('.'):
+            if os.path.isdir(path):
+                for subfn in os.listdir(path):
+                    if not subfn.startswith('.'):
+                        os.unlink(os.path.join(path, subfn))
+                os.rmdir(path)
 
 
 class Test(unittest.TestCase):