diff --git a/tools/python/xen/xend/XendDomainInfo.py b/tools/python/xen/xend/XendDomainInfo.py
index 0aa71fc4e6..5488b17f8f 100644
--- a/tools/python/xen/xend/XendDomainInfo.py
+++ b/tools/python/xen/xend/XendDomainInfo.py
@@ -1709,8 +1709,10 @@ class XendDomainInfo:
 
         dom =  XendDomain.instance().domain_lookup_nr(name)
         if dom and dom.info['uuid'] != self.info['uuid']:
-            raise VmError("VM name '%s' already exists as domain %s" %
-                          (name, str(dom.domid)))
+            raise VmError("VM name '%s' already exists%s" %
+                          (name,
+                           dom.domid is not None and
+                           ("as domain %s" % str(dom.domid)) or ""))
         
 
     def update(self, info = None, refresh = True):