diff --git a/app.js b/app.js
index 8d6cadf..8ba9257 100644
--- a/app.js
+++ b/app.js
@@ -20,6 +20,7 @@ process.on('SIGTERM', gracefulShutdown);
 // listen for INT signal e.g. Ctrl-C
 process.on('SIGINT', gracefulShutdown);
 
+// listen for shutdown signal from pm2
 process.on('message', function(msg) {
 	if (msg == 'shutdown')
 		gracefulShutdown();