diff --git a/lib/auth.js b/lib/auth.js
index ef1d646..dd6a54e 100644
--- a/lib/auth.js
+++ b/lib/auth.js
@@ -1,3 +1,4 @@
+'use strict'
 // auth
 // external modules
 var passport = require('passport')
diff --git a/lib/config.js b/lib/config.js
index af4c22c..2ecb478 100644
--- a/lib/config.js
+++ b/lib/config.js
@@ -1,3 +1,4 @@
+'use strict'
 // external modules
 var fs = require('fs')
 var path = require('path')
diff --git a/lib/history.js b/lib/history.js
index 69337dc..ffed3b9 100644
--- a/lib/history.js
+++ b/lib/history.js
@@ -1,3 +1,4 @@
+'use strict'
 // history
 // external modules
 
diff --git a/lib/letter-avatars.js b/lib/letter-avatars.js
index 92bd36e..7ba336b 100644
--- a/lib/letter-avatars.js
+++ b/lib/letter-avatars.js
@@ -1,3 +1,4 @@
+'use strict'
 // external modules
 var randomcolor = require('randomcolor')
 
diff --git a/lib/logger.js b/lib/logger.js
index 23e302d..2111d69 100644
--- a/lib/logger.js
+++ b/lib/logger.js
@@ -1,3 +1,4 @@
+'use strict'
 var winston = require('winston')
 winston.emitErrs = true
 
diff --git a/lib/migrations/20160515114000-user-add-tokens.js b/lib/migrations/20160515114000-user-add-tokens.js
index 20c0e03..4f05188 100644
--- a/lib/migrations/20160515114000-user-add-tokens.js
+++ b/lib/migrations/20160515114000-user-add-tokens.js
@@ -1,3 +1,4 @@
+'use strict'
 module.exports = {
   up: function (queryInterface, Sequelize) {
     queryInterface.addColumn('Users', 'accessToken', Sequelize.STRING)
diff --git a/lib/migrations/20160607060246-support-revision.js b/lib/migrations/20160607060246-support-revision.js
index 618bb4d..114aec2 100644
--- a/lib/migrations/20160607060246-support-revision.js
+++ b/lib/migrations/20160607060246-support-revision.js
@@ -1,3 +1,4 @@
+'use strict'
 module.exports = {
   up: function (queryInterface, Sequelize) {
     queryInterface.addColumn('Notes', 'savedAt', Sequelize.DATE)
diff --git a/lib/migrations/20160703062241-support-authorship.js b/lib/migrations/20160703062241-support-authorship.js
index 98381d4..a1d695e 100644
--- a/lib/migrations/20160703062241-support-authorship.js
+++ b/lib/migrations/20160703062241-support-authorship.js
@@ -1,3 +1,4 @@
+'use strict'
 module.exports = {
   up: function (queryInterface, Sequelize) {
     queryInterface.addColumn('Notes', 'authorship', Sequelize.TEXT)
diff --git a/lib/migrations/20161009040430-support-delete-note.js b/lib/migrations/20161009040430-support-delete-note.js
index 984920b..6e6fa20 100644
--- a/lib/migrations/20161009040430-support-delete-note.js
+++ b/lib/migrations/20161009040430-support-delete-note.js
@@ -1,3 +1,4 @@
+'use strict'
 module.exports = {
   up: function (queryInterface, Sequelize) {
     queryInterface.addColumn('Notes', 'deletedAt', Sequelize.DATE)
diff --git a/lib/migrations/20161201050312-support-email-signin.js b/lib/migrations/20161201050312-support-email-signin.js
index a97d3be..1f3abb1 100644
--- a/lib/migrations/20161201050312-support-email-signin.js
+++ b/lib/migrations/20161201050312-support-email-signin.js
@@ -1,3 +1,4 @@
+'use strict'
 module.exports = {
   up: function (queryInterface, Sequelize) {
     queryInterface.addColumn('Users', 'email', Sequelize.TEXT)
diff --git a/lib/models/author.js b/lib/models/author.js
index 5e39c34..8b4f74e 100644
--- a/lib/models/author.js
+++ b/lib/models/author.js
@@ -1,3 +1,4 @@
+'use strict'
 // external modules
 var Sequelize = require('sequelize')
 
diff --git a/lib/models/index.js b/lib/models/index.js
index 96babc2..a378ee6 100644
--- a/lib/models/index.js
+++ b/lib/models/index.js
@@ -1,3 +1,4 @@
+'use strict'
 // external modules
 var fs = require('fs')
 var path = require('path')
diff --git a/lib/models/note.js b/lib/models/note.js
index bef9ee2..dd5de8a 100644
--- a/lib/models/note.js
+++ b/lib/models/note.js
@@ -1,3 +1,4 @@
+'use strict'
 // external modules
 var fs = require('fs')
 var path = require('path')
diff --git a/lib/models/revision.js b/lib/models/revision.js
index d8dab30..581e7ea 100644
--- a/lib/models/revision.js
+++ b/lib/models/revision.js
@@ -1,3 +1,4 @@
+'use strict'
 // external modules
 var Sequelize = require('sequelize')
 var async = require('async')
diff --git a/lib/models/temp.js b/lib/models/temp.js
index e770bb3..2ad23fb 100644
--- a/lib/models/temp.js
+++ b/lib/models/temp.js
@@ -1,3 +1,4 @@
+'use strict'
 // external modules
 var shortId = require('shortid')
 
diff --git a/lib/models/user.js b/lib/models/user.js
index f7e533b..042b0d2 100644
--- a/lib/models/user.js
+++ b/lib/models/user.js
@@ -1,3 +1,4 @@
+'use strict'
 // external modules
 var md5 = require('blueimp-md5')
 var Sequelize = require('sequelize')
diff --git a/lib/realtime.js b/lib/realtime.js
index cff795c..618fdad 100644
--- a/lib/realtime.js
+++ b/lib/realtime.js
@@ -1,3 +1,4 @@
+'use strict'
 // realtime
 // external modules
 var cookie = require('cookie')
diff --git a/lib/response.js b/lib/response.js
index 31fa18b..13a94bb 100755
--- a/lib/response.js
+++ b/lib/response.js
@@ -1,3 +1,4 @@
+'use strict'
 // response
 // external modules
 var fs = require('fs')
diff --git a/lib/workers/dmpWorker.js b/lib/workers/dmpWorker.js
index 6a1da98..b0ed0f4 100644
--- a/lib/workers/dmpWorker.js
+++ b/lib/workers/dmpWorker.js
@@ -1,3 +1,4 @@
+'use strict'
 // external modules
 var DiffMatchPatch = require('diff-match-patch')
 var dmp = new DiffMatchPatch()