diff --git a/priv/emqx.schema b/priv/emqx.schema
index caa0a2258..25589f138 100644
--- a/priv/emqx.schema
+++ b/priv/emqx.schema
@@ -1672,7 +1672,7 @@ end}.
                (Opt, Val, Opts) ->
                   case IsSsl(Opt) of
                       true ->
-                          SslOpts = Parse(Opt, Val) ++ [proplists:get_value(ssl_opts, Opts, [])],
+                          SslOpts = Parse(Opt, Val) ++ proplists:get_value(ssl_opts, Opts, []),
                           lists:ukeymerge(1, [{ssl_opts, SslOpts}], lists:usort(Opts));
                       false ->
                           [{Opt, Val}|Opts]
diff --git a/src/emqx_bridge.erl b/src/emqx_bridge.erl
index af85df68e..cdb4183fd 100644
--- a/src/emqx_bridge.erl
+++ b/src/emqx_bridge.erl
@@ -345,10 +345,10 @@ connected(internal, maybe_send, State) ->
             {next_state, connecting, disconnect(NewState)}
     end;
 connected(info, {disconnected, ConnRef, Reason},
-          #{conn_ref := ConnRefCurrent, connection := Conn} = State) ->
+          #{conn_ref := ConnRefCurrent} = State) ->
     case ConnRefCurrent =:= ConnRef of
         true ->
-            ?LOG(info, "Bridge ~p diconnected~nreason=~p", [name(), Conn, Reason]),
+            ?LOG(info, "Bridge ~p diconnected~nreason=~p", [name(), Reason]),
             {next_state, connecting,
              State#{conn_ref := undefined, connection := undefined}};
         false ->
diff --git a/src/emqx_message.erl b/src/emqx_message.erl
index f2b821884..25e6492bd 100644
--- a/src/emqx_message.erl
+++ b/src/emqx_message.erl
@@ -81,11 +81,12 @@ unset_flag(Flag, Msg = #message{flags = Flags}) ->
         false -> Msg
     end.
 
--spec(set_headers(map(), emqx_types:message()) -> emqx_types:message()).
+-spec(set_headers(undefined | map(), emqx_types:message()) -> emqx_types:message()).
 set_headers(Headers, Msg = #message{headers = undefined}) when is_map(Headers) ->
     Msg#message{headers = Headers};
 set_headers(New, Msg = #message{headers = Old}) when is_map(New) ->
-    Msg#message{headers = maps:merge(Old, New)}.
+    Msg#message{headers = maps:merge(Old, New)};
+set_headers(undefined, Msg) -> Msg.
 
 -spec(get_header(term(), emqx_types:message()) -> term()).
 get_header(Hdr, Msg) ->