diff --git a/src/common/xmpp/stringprepare.py b/src/common/xmpp/stringprepare.py
index bae16fcec..657895c84 100644
--- a/src/common/xmpp/stringprepare.py
+++ b/src/common/xmpp/stringprepare.py
@@ -2,7 +2,7 @@
 ## src/common/xmpp/stringprepare.py
 ##
 ## Copyright (C) 2001-2005 Twisted Matrix Laboratories
-## Copyright (C) 2005-2010 Yann Leboulanger <asterix AT lagaule.org>
+## Copyright (C) 2005-2011 Yann Leboulanger <asterix AT lagaule.org>
 ## Copyright (C) 2006 Stefan Bethge <stefan AT lanpartei.de>
 ## Copyright (C) 2007 Jean-Marie Traissard <jim AT lapin.org>
 ##
@@ -202,6 +202,8 @@ class NamePrep:
     def nameprep(self, label):
         label = idna.nameprep(label)
         self.check_prohibiteds(label)
+        if len(label) == 0:
+            raise UnicodeError, "Invalid empty name"
         if label[0] == '-':
             raise UnicodeError, "Invalid leading hyphen-minus"
         if label[-1] == '-':