diff --git a/Lib/smtpd.py b/Lib/smtpd.py
index c656ec7..4aa3476 100755
--- a/Lib/smtpd.py
+++ b/Lib/smtpd.py
@@ -221,7 +221,7 @@
 
     def smtp_MAIL(self, arg):
         print >> DEBUGSTREAM, '===> MAIL', arg
-        address = self.__getaddr('FROM:', arg)
+        address = self.__getaddr('FROM:', arg) if arg else None
         if not address:
             self.push('501 Syntax: MAIL FROM:<address>')
             return