diff --git a/lib/objects.py b/lib/objects.py
index d59f41754b01b50a981e998a83ef848c76c4ebb2..90e9a6af965b52e1f0cf2f9e096294bf23e2544e 100644
--- a/lib/objects.py
+++ b/lib/objects.py
@@ -41,6 +41,8 @@ from cStringIO import StringIO
 from ganeti import errors
 from ganeti import constants
 
+from socket import AF_INET
+
 
 __all__ = ["ConfigObject", "ConfigData", "NIC", "Disk", "Instance",
            "OS", "Node", "Cluster", "FillDict"]
@@ -985,6 +987,10 @@ class Cluster(TaggableObject):
     if self.reserved_lvs is None:
       self.reserved_lvs = []
 
+    # primary_ip_family added before 2.3
+    if self.primary_ip_family is None:
+      self.primary_ip_family = AF_INET
+
   def ToDict(self):
     """Custom function for cluster.