diff --git a/lib/objects.py b/lib/objects.py
index 51ef992cf6e7345b7c149412db4d01eeae975af4..cde0779cfa90b17e0ce02c4ce4447132778a9253 100644
--- a/lib/objects.py
+++ b/lib/objects.py
@@ -339,6 +339,10 @@ class NIC(ConfigObject):
       if self.bridge is not None:
         self.nicparams[constants.NIC_MODE] = constants.NIC_MODE_BRIDGED
         self.nicparams[constants.NIC_LINK] = self.bridge
+    # bridge is no longer used it 2.1. The slot is left there to support
+    # upgrading, but will be removed in 2.2
+    if self.bridge is not None:
+      self.bridge = None
 
 
 class Disk(ConfigObject):
@@ -822,6 +826,11 @@ class Cluster(TaggableObject):
     if self.modify_etc_hosts is None:
       self.modify_etc_hosts = True
 
+    # default_bridge is no longer used it 2.1. The slot is left there to
+    # support auto-upgrading, but will be removed in 2.2
+    if self.default_bridge is not None:
+      self.default_bridge = None
+
   def ToDict(self):
     """Custom function for cluster.