diff --git a/server/helpers.js b/server/helpers.js
index 12d5a06..f4d0b6e 100644
--- a/server/helpers.js
+++ b/server/helpers.js
@@ -1,3 +1,4 @@
+"use strict"
 const ROLE_MEMBER = require('./constants').ROLE_MEMBER;
 const ROLE_CLIENT = require('./constants').ROLE_CLIENT;
 const ROLE_OWNER = require('./constants').ROLE_OWNER;
diff --git a/server/index.js b/server/index.js
index 78ed52b..cb5c65f 100644
--- a/server/index.js
+++ b/server/index.js
@@ -1,3 +1,4 @@
+"use strict"
 // Importing Node modules and initializing Express
 const express = require('express'),
   app = express(),
diff --git a/server/router.js b/server/router.js
index fe65b8f..77ed9b9 100644
--- a/server/router.js
+++ b/server/router.js
@@ -1,3 +1,4 @@
+"use strict"
 const AuthenticationController = require('./controllers/authentication');
 const UserController = require('./controllers/user');
 const ChatController = require('./controllers/chat');