diff --git a/app.js b/app.js
index 23a97ca..c68de67 100644
--- a/app.js
+++ b/app.js
@@ -28,12 +28,11 @@ io.on('connection', (socket) => {
 
 	//When client requests for setting username
 	socket.on('set username', (name) => {
-		name = name.trim()
+		name = (name || "").trim()
 
 		//if name is empty(null), do nothing
-		if(name == "" || name == null) {
-			return;
-		}
+		if(!name) return socket.emit('user invalid', {username: `${name} is invalid.`});
+		
 		//if username is not taken
 		else if(rooms[0].users.indexOf(name) == -1) {
 			rooms[0].users.push(name);
@@ -199,3 +198,5 @@ io.on('connection', (socket) => {
 
 	});
 });
+
+module.exports = app;