diff --git a/Lib/smtpd.py b/Lib/smtpd.py
index 0fae1702a67..69cdcdc4468 100755
--- a/Lib/smtpd.py
+++ b/Lib/smtpd.py
@@ -462,7 +462,7 @@ class SMTPChannel(asynchat.async_chat):
 
     def smtp_HELP(self, arg):
         if arg:
-            extended = ' [SP <mail parameters]'
+            extended = ' [SP <mail-parameters>]'
             lc_arg = arg.upper()
             if lc_arg == 'EHLO':
                 self.push('250 Syntax: EHLO hostname')