diff --git a/.travis.yml b/.travis.yml
index 95dc2aa0..10612c46 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,6 +4,3 @@ node_js:
   - stable
   - "8"
   - "6"
-  - "4"
-install:
-  - YARN_IGNORE_ENGINES=true yarn
diff --git a/cli.js b/cli.js
index efb45a69..f38c7371 100755
--- a/cli.js
+++ b/cli.js
@@ -1,5 +1,4 @@
 #!/usr/bin/env node
-'use strict'
 
 const ciJobNumber = require('ci-job-number')
 const cosmiconfig = require('cosmiconfig')
diff --git a/index.js b/index.js
index 65e69192..59f50f51 100644
--- a/index.js
+++ b/index.js
@@ -1,5 +1,3 @@
-'use strict'
-
 const escapeRegexp = require('escape-string-regexp')
 const Compression = require('compression-webpack-plugin')
 const Analyzer = require('webpack-bundle-analyzer').BundleAnalyzerPlugin
diff --git a/package.json b/package.json
index 416092ee..25c8f034 100644
--- a/package.json
+++ b/package.json
@@ -58,14 +58,15 @@
     "test": "jest && yarn run lint && yarn run spellcheck"
   },
   "engines": {
-    "node": ">=4.0.0"
+    "node": ">=6.11.5"
   },
   "eslintConfig": {
     "extends": "eslint-config-logux/node4",
     "rules": {
       "security/detect-non-literal-require": "off",
       "security/detect-non-literal-regexp": "off",
-      "global-require": "off"
+      "global-require": "off",
+      "strict": "off"
     }
   },
   "jest": {
diff --git a/test/cli.test.js b/test/cli.test.js
index 2822603d..36ef1686 100644
--- a/test/cli.test.js
+++ b/test/cli.test.js
@@ -1,5 +1,3 @@
-'use strict'
-
 const spawn = require('cross-spawn')
 const path = require('path')
 
diff --git a/test/index.test.js b/test/index.test.js
index ad70824e..ead3eae2 100644
--- a/test/index.test.js
+++ b/test/index.test.js
@@ -1,5 +1,3 @@
-'use strict'
-
 const path = require('path')
 
 const getSize = require('../')