diff -r d6d15fcf5eb6 Lib/sre_parse.py
--- a/Lib/sre_parse.py	Mon Nov 21 18:04:30 2011 +0100
+++ b/Lib/sre_parse.py	Mon Nov 21 20:28:48 2011 -0500
@@ -222,6 +222,8 @@
 
 def isname(name):
     # check that group name is a valid string
+    if name == "":
+        return False
     if not isident(name[0]):
         return False
     for char in name[1:]: