--- a/rollbot.py	Mon May 09 21:25:51 2016 +0800
+++ b/rollbot.py	Mon May 09 21:51:10 2016 +0800
@@ -44,7 +44,10 @@
     parser.add_argument('-j', '--jid', dest='jid', help='JID to use')
     parser.add_argument('-p', '--password', dest='password', help='password to use')
     parser.add_argument('-n', '--nick', dest='nick', help='MUC nickname', default='rollbot')
-    parser.add_argument('-d', '--debug', help='set logging to DEBUG', action='store_const', dest='loglevel', const=logging.DEBUG, default=logging.INFO)
+
+    group = parser.add_mutually_exclusive_group()
+    group.add_argument('-q', '--quiet', help='set logging to ERROR', action='store_const', dest='loglevel', const=logging.ERROR, default=logging.INFO)
+    group.add_argument('-d', '--debug', help='set logging to DEBUG', action='store_const', dest='loglevel', const=logging.DEBUG, default=logging.INFO)
 
     args = parser.parse_args()