diff --git a/lib/utils/config/getServerlessDir.js b/lib/utils/config/getServerlessDir.js
index a5d8cc461..792acab7f 100644
--- a/lib/utils/config/getServerlessDir.js
+++ b/lib/utils/config/getServerlessDir.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const path = require('path');
 const os = require('os');
 
diff --git a/lib/utils/config/update.js b/lib/utils/config/update.js
index 237d195a1..d97c43cf4 100644
--- a/lib/utils/config/update.js
+++ b/lib/utils/config/update.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const path = require('path');
 const getServerlessDir = require('./getServerlessDir');
 const writeFileSync = require('../fs/writeFileSync');
diff --git a/lib/utils/fs/fileExistsSync.js b/lib/utils/fs/fileExistsSync.js
index f0d6862a0..147300e7b 100644
--- a/lib/utils/fs/fileExistsSync.js
+++ b/lib/utils/fs/fileExistsSync.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const fse = require('./fse');
 
 function fileExistsSync(filePath) {
diff --git a/lib/utils/fs/fse.js b/lib/utils/fs/fse.js
index 97ef536ce..c1428e286 100644
--- a/lib/utils/fs/fse.js
+++ b/lib/utils/fs/fse.js
@@ -1,6 +1,8 @@
 /**
  * Promisified FSE
  */
+'use strict';
+
 const BbPromise = require('bluebird');
 const fse = BbPromise.promisifyAll(require('fs-extra'));
 
diff --git a/lib/utils/fs/readFileSync.js b/lib/utils/fs/readFileSync.js
index c286f998a..7d341b4c7 100644
--- a/lib/utils/fs/readFileSync.js
+++ b/lib/utils/fs/readFileSync.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const YAML = require('js-yaml');
 const fse = require('./fse');
 
diff --git a/lib/utils/fs/readFileSync.test.js b/lib/utils/fs/readFileSync.test.js
index 6a0252bac..652432040 100644
--- a/lib/utils/fs/readFileSync.test.js
+++ b/lib/utils/fs/readFileSync.test.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const testUtils = require('../../../tests/utils');
 const expect = require('chai').expect;
 const writeFileSync = require('./writeFileSync');
diff --git a/lib/utils/fs/writeFileSync.js b/lib/utils/fs/writeFileSync.js
index f393a0516..e9fefae59 100644
--- a/lib/utils/fs/writeFileSync.js
+++ b/lib/utils/fs/writeFileSync.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const path = require('path');
 const YAML = require('js-yaml');
 const fse = require('./fse');
diff --git a/lib/utils/fs/writeFileSync.test.js b/lib/utils/fs/writeFileSync.test.js
index cc33dbf61..5a685e263 100644
--- a/lib/utils/fs/writeFileSync.test.js
+++ b/lib/utils/fs/writeFileSync.test.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const testUtils = require('../../../tests/utils');
 const Serverless = require('../../../lib/Serverless');
 const expect = require('chai').expect;
diff --git a/lib/utils/getFrameworkId.js b/lib/utils/getFrameworkId.js
index 90fbde0be..c9f034023 100644
--- a/lib/utils/getFrameworkId.js
+++ b/lib/utils/getFrameworkId.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const path = require('path');
 const getServerlessDir = require('./config/getServerlessDir');
 const readFileSync = require('./fs/readFileSync');