Index: Lib/imaplib.py
===================================================================
--- Lib/imaplib.py	(revision 83699)
+++ Lib/imaplib.py	(working copy)
@@ -146,7 +146,7 @@
     class abort(error): pass        # Service errors - close and retry
     class readonly(abort): pass     # Mailbox status changed to READ-ONLY
 
-    mustquote = re.compile(r"[^\w!#$%&'*+,.:;<=>?^`|~-]")
+    mustquote = re.compile(r'[()\s%*"]|"{"|"\\"|"\]"')
 
     def __init__(self, host = '', port = IMAP4_PORT):
         self.debug = Debug