diff --git a/lib/objects.py b/lib/objects.py
index bb7c1c8624a6d187bd965be95cefea2e4334497f..d67e31cf2182234b1d72d3e6ad0ef07ac23867f7 100644
--- a/lib/objects.py
+++ b/lib/objects.py
@@ -688,7 +688,6 @@ class Node(TaggableObject):
 class Cluster(TaggableObject):
   """Config object representing the cluster."""
   __slots__ = TaggableObject.__slots__ + [
-    "config_version",
     "serial_no",
     "rsahostkeypub",
     "highest_used_port",