diff --git a/mercurial/fileset.py b/mercurial/fileset.py
--- a/mercurial/fileset.py
+++ b/mercurial/fileset.py
@@ -14,6 +14,7 @@ from . import (
     error,
     merge,
     parser,
+    pycompat,
     registrar,
     scmutil,
     util,
@@ -43,6 +44,7 @@ globchars = ".*{}[]?/\\_"
 
 def tokenize(program):
     pos, l = 0, len(program)
+    program = pycompat.bytestr(program)
     while pos < l:
         c = program[pos]
         if c.isspace(): # skip inter-token whitespace