diff -r 092a15aa2430 tools/python/xen/xend/XendAPIStore.py
--- a/tools/python/xen/xend/XendAPIStore.py	Fri Jul 18 15:03:55 2008 +0100
+++ b/tools/python/xen/xend/XendAPIStore.py	Fri Jul 25 15:00:23 2008 +0900
@@ -33,7 +33,8 @@ def register(uuid, type, inst):
 
 def deregister(uuid, type):
     old = get(uuid, type)
-    del __classes[(uuid, type)]
+    if old is not None:
+        del __classes[(uuid, type)]
     return old
 
 def get(uuid, type):