diff --git a/rel/files/app.config b/rel/files/app.config
index 86ef3a181..a0650e360 100644
--- a/rel/files/app.config
+++ b/rel/files/app.config
@@ -19,7 +19,7 @@
 	{handlers, [
 		{lager_console_backend, info},
 		{lager_file_backend, [
-            {formatter_config, [time, " [",severity,"] ", message, "\n"]},
+            {formatter_config, [time, " ", pid, " [",severity,"] ", message, "\n"]},
 			{file, "log/emqttd_info.log"},
 			{level, info},
 			{size, 104857600},
@@ -27,7 +27,7 @@
 			{count, 10}
 		]},
 		{lager_file_backend, [
-            {formatter_config, [time, " [",severity,"] ", message, "\n"]},
+            {formatter_config, [time, " ", pid, " [",severity,"] ", message, "\n"]},
 			{file, "log/emqttd_error.log"},
 			{level, error},
 			{size, 10485760},