diff --git a/CHANGES.md b/CHANGES.md
index 473c6996..1f9a57c6 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -5,6 +5,10 @@
 - postcss-loader: v1.2.1 → [v1.2.2](https://github.com/postcss/postcss-loader/blob/master/CHANGELOG.md#122)
 - webpack-merge: v2.3.1 → [v2.4.0](https://github.com/survivejs/webpack-merge/blob/master/CHANGELOG.md#240--2017-01-12)
 
+**Internal:**
+
+- Use ES2015 `String` methods available in Node.js v4 instead of `String.prototype.indexOf` comparisons.
+
 # 0.14.1 / 2017-01-13
 
 **Fixed:**
diff --git a/src/createWebpackConfig.js b/src/createWebpackConfig.js
index b3861ba2..dea6f0c5 100644
--- a/src/createWebpackConfig.js
+++ b/src/createWebpackConfig.js
@@ -15,7 +15,7 @@ import merge from 'webpack-merge'
 import HashedModuleIdsPlugin from '../vendor/HashedModuleIdsPlugin'
 import createBabelConfig from './createBabelConfig'
 import debug from './debug'
-import {deepToString, endsWith, typeOf} from './utils'
+import {deepToString, typeOf} from './utils'
 import StatusPlugin from './WebpackStatusPlugin'
 
 // Top-level property names reserved for webpack config
@@ -69,7 +69,7 @@ export let loaderConfigFactory = (buildConfig, userConfig) =>
  */
 export let styleLoaderName = (prefix) =>
   (name) => {
-    if (prefix && endsWith(prefix, name)) {
+    if (prefix && prefix.endsWith(name)) {
       return prefix
     }
     return prefix ? `${prefix}-${name}` : name
@@ -254,7 +254,7 @@ function injectManifestPlugin() {
   this.plugin('compilation', (compilation) => {
     compilation.plugin('html-webpack-plugin-before-html-processing', (data, cb) => {
       Object.keys(compilation.assets).forEach(key => {
-        if (key.indexOf('manifest.') !== 0) return
+        if (!key.startsWith('manifest.')) return
         let {children} = compilation.assets[key]
         if (children && children[0]) {
           data.html = data.html.replace(
@@ -346,7 +346,7 @@ export function createPlugins(server, buildConfig = {}, userConfig = {}) {
         minChunks(module, count) {
           return (
             module.resource &&
-            module.resource.indexOf('node_modules') !== -1
+            module.resource.includes('node_modules')
           )
         }
       }))
diff --git a/src/utils.js b/src/utils.js
index adde4eff..427acffa 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -55,13 +55,6 @@ export function deepToString(object) {
   return util.inspect(object, {colors: true, depth: null})
 }
 
-/**
- * String.prototype.endsWith() is behind the --harmony flag in Node.js v0.12.
- */
-export function endsWith(s1, s2) {
-  return s1.lastIndexOf(s2) === s1.length - s2.length
-}
-
 /**
  * Get a list of nwb plugin names passed as arguments.
  * @param {Object} args parsed arguments.
diff --git a/src/webpackUtils.js b/src/webpackUtils.js
index cff40624..5c1e9981 100644
--- a/src/webpackUtils.js
+++ b/src/webpackUtils.js
@@ -57,7 +57,7 @@ function formatMessage(message) {
 }
 
 function isLikelyASyntaxError(message) {
-  return message.indexOf(FRIENDLY_SYNTAX_ERROR_LABEL) !== -1
+  return message.includes(FRIENDLY_SYNTAX_ERROR_LABEL)
 }
 
 function formatMessages(messages, type) {