diff --git a/lib/cmdlib.py b/lib/cmdlib.py
index d41cf83b3fd27d491b49ae310106d49b229721e0..9d3b9a509aa34981ba22bd1825d67900bd00d1e3 100644
--- a/lib/cmdlib.py
+++ b/lib/cmdlib.py
@@ -2503,7 +2503,7 @@ class LURenameInstance(LogicalUnit):
     instance_list = self.cfg.GetInstanceList()
     if new_name in instance_list:
       raise errors.OpPrereqError("Instance '%s' is already in the cluster" %
-                                 instance_name)
+                                 new_name)
 
     if not getattr(self.op, "ignore_ip", False):
       command = ["fping", "-q", name_info.ip]