diff --git a/Lib/lib2to3/pgen2/token.py b/Lib/lib2to3/pgen2/token.py
index 61468b3..1c81065 100755
--- a/Lib/lib2to3/pgen2/token.py
+++ b/Lib/lib2to3/pgen2/token.py
@@ -67,7 +67,7 @@
 #--end constants--
 
 tok_name = {}
-for _name, _value in globals().items():
+for _name, _value in list(globals().items()):
     if type(_value) is type(0):
         tok_name[_value] = _name