diff -r 570b0fd72cf8 -r d34fa1090221 pvl/hosts/host.py
--- a/pvl/hosts/host.py	Mon Mar 02 19:35:52 2015 +0200
+++ b/pvl/hosts/host.py	Mon Mar 02 19:36:10 2015 +0200
@@ -139,6 +139,9 @@
         return False
 
 def parse_dict(value, parse):
+    if not value:
+        return { }
+
     if isinstance(value, dict):
         values = value
     else:
@@ -158,14 +161,14 @@
     @classmethod
     def build (cls, name, domain,
             ip=None, ip6=None,
-            ethernet={ },
+            ethernet=None,
             owner=None,
             location=None,
             alias=None, alias4=None, alias6=None,
             forward=None, reverse=None,
             down=None,
             boot=None,
-            extensions=None,
+            extensions={ },
     ) :
         """
             Return a Host initialized from data attributes.