diff --git a/apps/emqx/src/emqx_congestion.erl b/apps/emqx/src/emqx_congestion.erl
index fa2788bc1..ca94ded90 100644
--- a/apps/emqx/src/emqx_congestion.erl
+++ b/apps/emqx/src/emqx_congestion.erl
@@ -20,6 +20,8 @@
         , cancel_alarms/3
         ]).
 
+-elvis([{elvis_style, invalid_dynamic_call, #{ignore => [emqx_congestion]}}]).
+
 -define(ALARM_CONN_CONGEST(Channel, Reason),
         list_to_binary(
           io_lib:format("~ts/~ts/~ts",
@@ -78,14 +80,14 @@ cancel_alarm_congestion(Socket, Transport, Channel, Reason) ->
 do_alarm_congestion(Socket, Transport, Channel, Reason) ->
     ok = update_alarm_sent_at(Reason),
     AlarmDetails = tcp_congestion_alarm_details(Socket, Transport, Channel),
-    Message = io_lib:format("connection congested: ~ts", [AlarmDetails]),
+    Message = io_lib:format("connection congested: ~0p", [AlarmDetails]),
     emqx_alarm:activate(?ALARM_CONN_CONGEST(Channel, Reason), AlarmDetails, Message),
     ok.
 
 do_cancel_alarm_congestion(Socket, Transport, Channel, Reason) ->
     ok = remove_alarm_sent_at(Reason),
     AlarmDetails = tcp_congestion_alarm_details(Socket, Transport, Channel),
-    Message = io_lib:format("connection congested: ~ts", [AlarmDetails]),
+    Message = io_lib:format("connection congested: ~0p", [AlarmDetails]),
     emqx_alarm:deactivate(?ALARM_CONN_CONGEST(Channel, Reason), AlarmDetails, Message),
     ok.
 
diff --git a/apps/emqx/test/emqx_connection_SUITE.erl b/apps/emqx/test/emqx_connection_SUITE.erl
index 5d2c31441..f96ac6ca7 100644
--- a/apps/emqx/test/emqx_connection_SUITE.erl
+++ b/apps/emqx/test/emqx_connection_SUITE.erl
@@ -335,7 +335,8 @@ t_handle_info(_) ->
 
 t_ensure_rate_limit(_) ->
     WhenOk = fun emqx_connection:next_incoming_msgs/3,
-    {ok, [], State} = emqx_connection:check_limiter([], [], WhenOk, [], st(#{limiter => undefined})),
+    {ok, [], State} = emqx_connection:check_limiter([], [], WhenOk, [],
+                                                    st(#{limiter => undefined})),
     ?assertEqual(undefined, emqx_connection:info(limiter, State)),
 
     Limiter = init_limiter(),
@@ -344,7 +345,8 @@ t_ensure_rate_limit(_) ->
 
     ok = meck:expect(emqx_htb_limiter, check,
                      fun(_, Client) -> {pause, 3000, undefined, Client} end),
-    {ok, State2} = emqx_connection:check_limiter([{1000, bytes_in}], [], WhenOk, [], st(#{limiter => Limiter})),
+    {ok, State2} = emqx_connection:check_limiter([{1000, bytes_in}], [],
+                                                 WhenOk, [], st(#{limiter => Limiter})),
     meck:unload(emqx_htb_limiter),
     ok = meck:new(emqx_htb_limiter, [passthrough, no_history, no_link]),
     ?assertNotEqual(undefined, emqx_connection:info(limiter_timer, State2)).
@@ -432,6 +434,32 @@ t_oom_shutdown(_) ->
       end, Opts),
     ok.
 
+t_cancel_congestion_alarm(_) ->
+    Opts = #{trap_exit => false},
+    ok = meck:expect(emqx_transport, getstat,
+                     fun(_Sock, [send_pend]) ->
+                             %% simulate congestion
+                             {ok, [{send_pend, 999}]};
+                        (_Sock, Options) ->
+                             {ok, [{K, 0} || K <- Options]}
+                     end),
+    with_conn(
+      fun(Pid) ->
+              #{ channel := Channel
+               , transport := Transport
+               , socket := Socket
+               } = emqx_connection:get_state(Pid),
+              %% precondition
+              Zone = emqx_channel:info(zone, Channel),
+              true = emqx_config:get_zone_conf(Zone, [conn_congestion, enable_alarm]),
+              %% should not raise errors
+              ok = emqx_congestion:maybe_alarm_conn_congestion(Socket, Transport, Channel),
+              %% should not raise errors either
+              ok = emqx_congestion:cancel_alarms(Socket, Transport, Channel),
+              ok
+      end, Opts),
+    ok.
+
 %%--------------------------------------------------------------------
 %% Helper functions
 %%--------------------------------------------------------------------
@@ -524,7 +552,10 @@ channel(InitFields) ->
     maps:fold(fun(Field, Value, Channel) ->
                 emqx_channel:set_field(Field, Value, Channel)
               end,
-              emqx_channel:init(ConnInfo, #{zone => default, limiter => limiter_cfg(), listener => {tcp, default}}),
+              emqx_channel:init(ConnInfo, #{ zone => default
+                                           , limiter => limiter_cfg()
+                                           , listener => {tcp, default}
+                                           }),
               maps:merge(#{clientinfo => ClientInfo,
                            session    => Session,
                            conn_state => connected