diff --git a/apps/emqx_auth_http/src/emqx_auth_http_app.erl b/apps/emqx_auth_http/src/emqx_auth_http_app.erl
index 2958b93ea..20f2c381e 100644
--- a/apps/emqx_auth_http/src/emqx_auth_http_app.erl
+++ b/apps/emqx_auth_http/src/emqx_auth_http_app.erl
@@ -150,7 +150,7 @@ ensure_content_type_header(Method, Headers)
   when Method =:= post orelse Method =:= put ->
     Headers;
 ensure_content_type_header(_Method, Headers) ->
-    lists:keydelete("content-type", 1, Headers).
+    lists:keydelete(<<"content-type">>, 1, Headers).
 
 path(#{path := "", 'query' := Query}) ->
     "?" ++ Query;
diff --git a/apps/emqx_auth_http/src/emqx_auth_http_cli.erl b/apps/emqx_auth_http/src/emqx_auth_http_cli.erl
index 5ef222ae5..d01f571e5 100644
--- a/apps/emqx_auth_http/src/emqx_auth_http_cli.erl
+++ b/apps/emqx_auth_http/src/emqx_auth_http_cli.erl
@@ -32,7 +32,7 @@ request(PoolName, get, Path, Headers, Params, Timeout) ->
     reply(ehttpc:request(PoolName, get, {NewPath, Headers}, Timeout));
 
 request(PoolName, post, Path, Headers, Params, Timeout) ->
-    Body = case proplists:get_value("content-type", Headers) of
+    Body = case proplists:get_value(<<"content-type">>, Headers) of
                "application/x-www-form-urlencoded" ->
                    cow_qs:qs(bin_kw(Params));
                "application/json" -> 
diff --git a/apps/emqx_web_hook/src/emqx_web_hook_actions.erl b/apps/emqx_web_hook/src/emqx_web_hook_actions.erl
index 79aefdb85..68e3e85d4 100644
--- a/apps/emqx_web_hook/src/emqx_web_hook_actions.erl
+++ b/apps/emqx_web_hook/src/emqx_web_hook_actions.erl
@@ -295,7 +295,7 @@ create_req(_, Path, Headers, Body) ->
 parse_action_params(Params = #{<<"url">> := URL}) ->
     {ok, #{path := CommonPath}} = emqx_http_lib:uri_parse(URL),
     Method = method(maps:get(<<"method">>, Params, <<"POST">>)),
-    Headers = headers(maps:get(<<"headers">>, Params, undefined)),
+    Headers = headers(maps:get(<<"headers">>, Params, #{})),
     NHeaders = ensure_content_type_header(Headers, Method),
     #{method => Method,
       path => merge_path(CommonPath, maps:get(<<"path">>, Params, <<>>)),
@@ -307,7 +307,7 @@ parse_action_params(Params = #{<<"url">> := URL}) ->
 ensure_content_type_header(Headers, Method) when Method =:= post orelse Method =:= put ->
     Headers;
 ensure_content_type_header(Headers, _Method) ->
-    lists:keydelete("content-type", 1, Headers).
+    lists:keydelete(<<"content-type">>, 1, Headers).
 
 merge_path(CommonPath, <<>>) ->
     l2b(CommonPath);
@@ -326,11 +326,8 @@ method(POST) when POST == <<"POST">>; POST == <<"post">> -> post;
 method(PUT) when PUT == <<"PUT">>; PUT == <<"put">> -> put;
 method(DEL) when DEL == <<"DELETE">>; DEL == <<"delete">> -> delete.
 
-headers(undefined) -> [];
-headers(Headers) when is_map(Headers) ->
-    headers(maps:to_list(Headers));
-headers(Headers) when is_list(Headers) ->
-    [{string:to_lower(str(K)), str(V)} || {K, V} <- Headers].
+headers(Headers) ->
+    emqx_http_lib:normalise_headers(maps:to_list(Headers)).
 
 str(Str) when is_list(Str) -> Str;
 str(Atom) when is_atom(Atom) -> atom_to_list(Atom);
diff --git a/apps/emqx_web_hook/src/emqx_web_hook_app.erl b/apps/emqx_web_hook/src/emqx_web_hook_app.erl
index 8265fa664..e728aca9d 100644
--- a/apps/emqx_web_hook/src/emqx_web_hook_app.erl
+++ b/apps/emqx_web_hook/src/emqx_web_hook_app.erl
@@ -87,7 +87,7 @@ translate_env() ->
     application:set_env(?APP, path, Path),
     application:set_env(?APP, pool_opts, PoolOpts),
     Headers = application:get_env(?APP, headers, []),
-    NHeaders = set_content_type(Headers),
+    NHeaders = set_content_type(emqx_http_lib:normalise_headers(Headers)),
     application:set_env(?APP, headers, NHeaders).
 
 path(#{path := "", 'query' := Query}) ->
@@ -100,5 +100,5 @@ path(#{path := Path}) ->
     Path.
 
 set_content_type(Headers) ->
-    NHeaders = proplists:delete(<<"Content-Type">>, proplists:delete(<<"content-type">>, Headers)),
+    NHeaders = proplists:delete(<<"content-type">>, Headers),
     [{<<"content-type">>, <<"application/json">>} | NHeaders].
diff --git a/src/emqx_http_lib.erl b/src/emqx_http_lib.erl
index 893c260ee..bf83eaea6 100644
--- a/src/emqx_http_lib.erl
+++ b/src/emqx_http_lib.erl
@@ -96,11 +96,11 @@ do_parse(URI) ->
 %% underscores replaced with hyphens
 %% NOTE: assuming the input Headers list is a proplists,
 %% that is, when a key is duplicated, list header overrides tail
-%% e.g. [{"Content_Type", "applicaiton/binary"}, {"content-type", "applicaiton/json"}]
+%% e.g. [{"Content_Type", "applicaiton/binary"}, {<<"content-type">>, "applicaiton/json"}]
 %% results in: [{"content-type", "applicaiton/binary"}]
 normalise_headers(Headers0) ->
     F = fun({K0, V}) ->
-                K = re:replace(K0, "_", "-", [{return,list}]),
+                K = re:replace(K0, "_", "-", [{return,binary}]),
                 {string:lowercase(K), V}
         end,
     Headers = lists:map(F, Headers0),
diff --git a/test/emqx_http_lib_tests.erl b/test/emqx_http_lib_tests.erl
index 7bcb7d056..54dd85d94 100644
--- a/test/emqx_http_lib_tests.erl
+++ b/test/emqx_http_lib_tests.erl
@@ -89,6 +89,6 @@ uri_parse_test_() ->
     ].
 
 normalise_headers_test() ->
-    ?assertEqual([{"content-type", "applicaiton/binary"}],
+    ?assertEqual([{<<"content-type">>, "applicaiton/binary"}],
                  emqx_http_lib:normalise_headers([{"Content_Type", "applicaiton/binary"},
                                                   {"content-type", "applicaiton/json"}])).