diff --git a/Lib/tokenize.py b/Lib/tokenize.py
--- a/Lib/tokenize.py
+++ b/Lib/tokenize.py
@@ -24,6 +24,7 @@
 __credits__ = ('GvR, ESR, Tim Peters, Thomas Wouters, Fred Drake, '
                'Skip Montanaro, Raymond Hettinger, Trent Nelson, '
                'Michael Foord')
+import builtins
 import re
 import sys
 from token import *
@@ -335,13 +336,11 @@
     return default, [first, second]
 
 
-_builtin_open = open
-
 def open(filename):
     """Open a file in read only mode using the encoding detected by
     detect_encoding().
     """
-    buffer = _builtin_open(filename, 'rb')
+    buffer = builtins.open(filename, 'rb')
     encoding, lines = detect_encoding(buffer.readline)
     buffer.seek(0)
     text = TextIOWrapper(buffer, encoding, line_buffering=True)