diff --git a/apps/njau_bot/src/http_handler/api_handler.erl b/apps/njau_bot/src/http_handler/api_handler.erl
index ff4d2a4..550b661 100644
--- a/apps/njau_bot/src/http_handler/api_handler.erl
+++ b/apps/njau_bot/src/http_handler/api_handler.erl
@@ -29,7 +29,7 @@ init(Req0, Opts) ->
             }, Resp, Req1),
             {ok, Req2, Opts};
         false ->
-            lager:debug("[api_handler] invalid sign: ~p, body sign: ~p, request body: ~ts", [Sign, BodySign, ReqBody]),
+            lager:debug("[api_handler] invalid sign: ~p, body sign: ~p, request body: ``~ts``", [Sign, BodySign, ReqBody]),
             Req2 = cowboy_req:reply(500, #{
                 <<"Content-Type">> => <<"text/html;charset=utf-8">>
             }, <<"Internal Server Error">>, Req1),