diff --git a/apps/emqx_gateway_coap/rebar.config b/apps/emqx_gateway_coap/rebar.config
index 3b070a72a..493ebe04f 100644
--- a/apps/emqx_gateway_coap/rebar.config
+++ b/apps/emqx_gateway_coap/rebar.config
@@ -1,3 +1,4 @@
+%% -*- mode: erlang -*-
 {erl_opts, [debug_info]}.
 {deps, [
     {emqx, {path, "../emqx"}},
diff --git a/apps/emqx_gateway_coap/src/emqx_gateway_coap.app.src b/apps/emqx_gateway_coap/src/emqx_gateway_coap.app.src
index 755532723..f9bc57722 100644
--- a/apps/emqx_gateway_coap/src/emqx_gateway_coap.app.src
+++ b/apps/emqx_gateway_coap/src/emqx_gateway_coap.app.src
@@ -1,3 +1,4 @@
+%% -*- mode: erlang -*-
 {application, emqx_gateway_coap, [
     {description, "CoAP Gateway"},
     {vsn, "0.1.4"},
diff --git a/apps/emqx_gateway_exproto/rebar.config b/apps/emqx_gateway_exproto/rebar.config
index 473fa9b67..aafbe4e13 100644
--- a/apps/emqx_gateway_exproto/rebar.config
+++ b/apps/emqx_gateway_exproto/rebar.config
@@ -1,3 +1,4 @@
+%% -*- mode: erlang -*-
 {erl_opts, [debug_info]}.
 {deps, [
     {emqx, {path, "../emqx"}},
diff --git a/apps/emqx_gateway_exproto/src/emqx_gateway_exproto.app.src b/apps/emqx_gateway_exproto/src/emqx_gateway_exproto.app.src
index 09622763b..890435d59 100644
--- a/apps/emqx_gateway_exproto/src/emqx_gateway_exproto.app.src
+++ b/apps/emqx_gateway_exproto/src/emqx_gateway_exproto.app.src
@@ -1,3 +1,4 @@
+%% -*- mode: erlang -*-
 {application, emqx_gateway_exproto, [
     {description, "ExProto Gateway"},
     {vsn, "0.1.4"},
diff --git a/apps/emqx_gateway_gbt32960/rebar.config b/apps/emqx_gateway_gbt32960/rebar.config
index cfeb0a195..456746d25 100644
--- a/apps/emqx_gateway_gbt32960/rebar.config
+++ b/apps/emqx_gateway_gbt32960/rebar.config
@@ -1,6 +1,7 @@
+%% -*- mode: erlang -*-
 {erl_opts, [debug_info]}.
 {deps, [
-  {emqx, {path, "../../apps/emqx"}},
-  {emqx_utils, {path, "../emqx_utils"}},
-  {emqx_gateway, {path, "../../apps/emqx_gateway"}}
+    {emqx, {path, "../../apps/emqx"}},
+    {emqx_utils, {path, "../emqx_utils"}},
+    {emqx_gateway, {path, "../../apps/emqx_gateway"}}
 ]}.
diff --git a/apps/emqx_gateway_gbt32960/src/emqx_gateway_gbt32960.app.src b/apps/emqx_gateway_gbt32960/src/emqx_gateway_gbt32960.app.src
index ee6cf30d8..0ed2dca39 100644
--- a/apps/emqx_gateway_gbt32960/src/emqx_gateway_gbt32960.app.src
+++ b/apps/emqx_gateway_gbt32960/src/emqx_gateway_gbt32960.app.src
@@ -1,3 +1,4 @@
+%% -*- mode: erlang -*-
 {application, emqx_gateway_gbt32960, [
     {description, "GBT32960 Gateway"},
     {vsn, "0.1.0"},
diff --git a/apps/emqx_gateway_lwm2m/rebar.config b/apps/emqx_gateway_lwm2m/rebar.config
index c8675c3ba..28c3c85e5 100644
--- a/apps/emqx_gateway_lwm2m/rebar.config
+++ b/apps/emqx_gateway_lwm2m/rebar.config
@@ -1,3 +1,4 @@
+%% -*- mode: erlang -*-
 {erl_opts, [debug_info]}.
 {deps, [ {emqx, {path, "../../apps/emqx"}},
          {emqx_gateway, {path, "../../apps/emqx_gateway"}}
diff --git a/apps/emqx_gateway_lwm2m/src/emqx_gateway_lwm2m.app.src b/apps/emqx_gateway_lwm2m/src/emqx_gateway_lwm2m.app.src
index e5afd7871..7e502632c 100644
--- a/apps/emqx_gateway_lwm2m/src/emqx_gateway_lwm2m.app.src
+++ b/apps/emqx_gateway_lwm2m/src/emqx_gateway_lwm2m.app.src
@@ -1,3 +1,4 @@
+%% -*- mode: erlang -*-
 {application, emqx_gateway_lwm2m, [
     {description, "LwM2M Gateway"},
     {vsn, "0.1.3"},
diff --git a/apps/emqx_gateway_mqttsn/src/emqx_gateway_mqttsn.app.src b/apps/emqx_gateway_mqttsn/src/emqx_gateway_mqttsn.app.src
index c2f6d642b..da7c45133 100644
--- a/apps/emqx_gateway_mqttsn/src/emqx_gateway_mqttsn.app.src
+++ b/apps/emqx_gateway_mqttsn/src/emqx_gateway_mqttsn.app.src
@@ -1,3 +1,4 @@
+%% -*- mode: erlang -*-
 {application, emqx_gateway_mqttsn, [
     {description, "MQTT-SN Gateway"},
     {vsn, "0.1.5"},
diff --git a/apps/emqx_gateway_stomp/rebar.config b/apps/emqx_gateway_stomp/rebar.config
index cfeb0a195..55e6f52f2 100644
--- a/apps/emqx_gateway_stomp/rebar.config
+++ b/apps/emqx_gateway_stomp/rebar.config
@@ -1,3 +1,4 @@
+%% -*- mode: erlang -*-
 {erl_opts, [debug_info]}.
 {deps, [
   {emqx, {path, "../../apps/emqx"}},
diff --git a/apps/emqx_gateway_stomp/src/emqx_gateway_stomp.app.src b/apps/emqx_gateway_stomp/src/emqx_gateway_stomp.app.src
index 22dd4efde..01d18b607 100644
--- a/apps/emqx_gateway_stomp/src/emqx_gateway_stomp.app.src
+++ b/apps/emqx_gateway_stomp/src/emqx_gateway_stomp.app.src
@@ -1,3 +1,4 @@
+%% -*- mode: erlang -*-
 {application, emqx_gateway_stomp, [
     {description, "Stomp Gateway"},
     {vsn, "0.1.3"},