diff --git a/src/emqx_message.erl b/src/emqx_message.erl
index 6fbd3bbf5..ca8a433d0 100644
--- a/src/emqx_message.erl
+++ b/src/emqx_message.erl
@@ -38,6 +38,7 @@
 %% Flags
 -export([ get_flag/2
         , get_flag/3
+        , get_flags/1
         , set_flag/2
         , set_flag/3
         , set_flags/2
@@ -85,6 +86,7 @@ make(From, QoS, Topic, Payload) when ?QOS_0 =< QoS, QoS =< ?QOS_2 ->
              qos = QoS,
              from = From,
              flags = #{dup => false},
+             headers = #{},
              topic = Topic,
              payload = Payload,
              timestamp = os:timestamp()}.
@@ -119,6 +121,9 @@ get_flag(Flag, Msg) ->
 get_flag(Flag, #message{flags = Flags}, Default) ->
     maps:get(Flag, Flags, Default).
 
+-spec(get_flags(emqx_types:message()) -> maybe(map())).
+get_flags(#message{flags = Flags}) -> Flags.
+
 -spec(set_flag(flag(), emqx_types:message()) -> emqx_types:message()).
 set_flag(Flag, Msg = #message{flags = undefined}) when is_atom(Flag) ->
     Msg#message{flags = #{Flag => true}};
@@ -144,8 +149,7 @@ unset_flag(Flag, Msg = #message{flags = Flags}) ->
 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)};
-set_headers(undefined, Msg) -> Msg.
+    Msg#message{headers = maps:merge(Old, New)}.
 
 -spec(get_headers(emqx_types:message()) -> map()).
 get_headers(Msg) ->