diff --git a/.travis.yml b/.travis.yml
index d7cb75d..07cfce7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,8 +5,7 @@ cache:
     - ~/.npm
 node_js:
   - "9"
-  - "6"
-  - "4"
+  - "7.6"
 after_success:
   - npm run travis-deploy-once "npm run semantic-release"
 branches:
diff --git a/index.js b/index.js
index 3d6c2f9..7f0795e 100644
--- a/index.js
+++ b/index.js
@@ -1,13 +1,13 @@
-var { inlineSource } = require('inline-source'),
-    PluginError = require('plugin-error'),
-    path = require('path'),
-    through = require('through2');
+'use strict';
+
+const { inlineSource } = require('inline-source');
+const PluginError = require('plugin-error');
+const path = require('path');
+const through = require('through2');
 
 const PLUGIN_NAME = 'gulp-inline-source';
 
 function gulpInlineSource (options) {
-    'use strict';
-
     return through.obj(function (file, enc, cb) {
         var self = this;
 
diff --git a/package.json b/package.json
index 756e835..37f7382 100644
--- a/package.json
+++ b/package.json
@@ -11,6 +11,9 @@
     "css",
     "javascript"
   ],
+  "engines": {
+    "node": ">=7.6"
+  },
   "scripts": {
     "test": "tape test/*.js | faucet",
     "commit": "git-cz",
diff --git a/test/main.js b/test/main.js
index 950f365..141e038 100644
--- a/test/main.js
+++ b/test/main.js
@@ -1,10 +1,10 @@
 'use strict';
 
-var path = require('path'),
-    Vinyl = require('vinyl'),
-    fs = require('fs'),
-    test = require('tape'),
-    inlinesource = require('../');
+const path = require('path');
+const Vinyl = require('vinyl');
+const fs = require('fs');
+const test = require('tape');
+const inlinesource = require('../');
 
 function getFile (filePath, contents) {
     return new Vinyl({
@@ -60,7 +60,7 @@ test('works with relative paths', function (t) {
 });
 
 test('inlines assets without minification', function (t) {
-    var stream = inlinesource({
+    const stream = inlinesource({
         compress: false
     });
 
@@ -69,17 +69,17 @@ test('inlines assets without minification', function (t) {
 
 test('throws when trying to compress non-ES5 syntax', function (t) {
     t.plan(1);
-    
-    var stream = inlinesource({ compress: true });
-    
+
+    const stream = inlinesource({ compress: true });
+
     stream.on('error', function (err) {
         t.pass();
     });
-    
+
     stream.on('finish', function () {
         t.end();
     });
-    
+
     stream.write(getFixture('script-es6.html'));
     stream.end();
 });