diff --git a/Lib/cgitb.py b/Lib/cgitb.py
index c65783f..33541fb 100644
--- a/Lib/cgitb.py
+++ b/Lib/cgitb.py
@@ -60,7 +60,7 @@
 def scanvars(reader, frame, locals):
     """Scan one logical line of Python and look up values of variables used."""
     import tokenize, keyword
-    vars, lasttoken, parent, prefix = [], None, None, ''
+    vars, lasttoken, parent, prefix, value = [], None, None, '', __UNDEF__
     for ttype, token, start, end, line in tokenize.generate_tokens(reader):
         if ttype == tokenize.NEWLINE: break
         if ttype == tokenize.NAME and token not in keyword.kwlist: