diff --git a/zulip_bots/zulip_bots/bots/xkcd/test_xkcd.py b/zulip_bots/zulip_bots/bots/xkcd/test_xkcd.py
index 310a8f5..3659bf1 100755
--- a/zulip_bots/zulip_bots/bots/xkcd/test_xkcd.py
+++ b/zulip_bots/zulip_bots/bots/xkcd/test_xkcd.py
@@ -13,7 +13,7 @@ class TestXkcdBot(BotTestCase):
     @mock.patch('logging.exception')
     def test_bot(self, mock_logging_exception):
         help_txt = "xkcd bot supports these commands:"
-        err_txt  = "xkcd bot only supports these commands:"
+        err_txt  = "xkcd bot only supports these commands, not `{}`:"
         commands = '''
 * `@xkcd help` to show this help message.
 * `@xkcd latest` to fetch the latest comic strip from xkcd.
@@ -78,7 +78,7 @@ class TestXkcdBot(BotTestCase):
             )
 
         # Empty query, no request made to the Internet.
-        bot_response = err_txt+commands
+        bot_response = err_txt.format('')+commands
         self.assert_bot_response(
             message = {'content': ''},
             response = {'content': bot_response},
@@ -94,7 +94,7 @@ class TestXkcdBot(BotTestCase):
         )
 
         # wrong command.
-        bot_response = err_txt+commands
+        bot_response = err_txt.format('x')+commands
         self.assert_bot_response(
             message = {'content': 'x'},
             response = {'content': bot_response},
diff --git a/zulip_bots/zulip_bots/bots/xkcd/xkcd.py b/zulip_bots/zulip_bots/bots/xkcd/xkcd.py
index 3d057be..7bccf7b 100644
--- a/zulip_bots/zulip_bots/bots/xkcd/xkcd.py
+++ b/zulip_bots/zulip_bots/bots/xkcd/xkcd.py
@@ -68,7 +68,7 @@ def get_xkcd_bot_response(message):
         elif command.isdigit():
             fetched = fetch_xkcd_query(XkcdBotCommand.COMIC_ID, command)
         else:
-            return commands_help % ('xkcd bot only supports these commands:')
+            return commands_help % ("xkcd bot only supports these commands, not `%s`:" % (command,))
     except (requests.exceptions.ConnectionError, XkcdServerError):
         logging.exception('Connection error occurred when trying to connect to xkcd server')
         return 'Sorry, I cannot process your request right now, please try again later!'