diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -177,8 +177,7 @@ keywords = set(['and', 'or', 'not'])
                       if c.isalnum() or c in '._@' or ord(c) > 127)
 
 # default set of valid characters for non-initial letters of symbols
-_symletters = set(c for c in [chr(i) for i in xrange(256)]
-                  if c.isalnum() or c in '-._/@' or ord(c) > 127)
+_symletters = _syminitletters | set('-/')
 
 def tokenize(program, lookup=None, syminitletters=None, symletters=None):
     '''