diff --git a/bind.js b/bind.js
index 413a17e..462ac45 100644
--- a/bind.js
+++ b/bind.js
@@ -1,10 +1,10 @@
-var hasOwn = {}.hasOwnProperty;
+const hasOwn = {}.hasOwnProperty;
 
 export default function classNames () {
-	var classes = '';
+	let classes = '';
 
-	for (var i = 0; i < arguments.length; i++) {
-		var arg = arguments[i];
+	for (let i = 0; i < arguments.length; i++) {
+		const arg = arguments[i];
 		if (arg) {
 			classes = appendClass(classes, parseValue.call(this, arg));
 		}
@@ -30,9 +30,9 @@ function parseValue (arg) {
 		return arg.toString();
 	}
 
-	var classes = '';
+	let classes = '';
 
-	for (var key in arg) {
+	for (const key in arg) {
 		if (hasOwn.call(arg, key) && arg[key]) {
 			classes = appendClass(classes, this && this[key] || key);
 		}
diff --git a/dedupe.js b/dedupe.js
index 61330d2..7de3f16 100644
--- a/dedupe.js
+++ b/dedupe.js
@@ -5,14 +5,14 @@ var classNames = (function () {
 	StorageObject.prototype = Object.create(null);
 
 	function _parseArray (resultSet, array) {
-		var length = array.length;
+		const length = array.length;
 
 		for (var i = 0; i < length; ++i) {
 			_parse(resultSet, array[i]);
 		}
 	}
 
-	var hasOwn = {}.hasOwnProperty;
+	const hasOwn = {}.hasOwnProperty;
 
 	function _parseNumber (resultSet, num) {
 		resultSet[num] = true;
@@ -24,7 +24,7 @@ var classNames = (function () {
 			return;
 		}
 
-		for (var k in object) {
+		for (const k in object) {
 			if (hasOwn.call(object, k)) {
 				// set value to false instead of deleting it to avoid changing object structure
 				// https://www.smashingmagazine.com/2012/11/writing-fast-memory-efficient-javascript/#de-referencing-misconceptions
@@ -33,19 +33,19 @@ var classNames = (function () {
 		}
 	}
 
-	var SPACE = /\s+/;
+	const SPACE = /\s+/;
 	function _parseString (resultSet, str) {
-		var array = str.split(SPACE);
-		var length = array.length;
+		const array = str.split(SPACE);
+		const length = array.length;
 
-		for (var i = 0; i < length; ++i) {
+		for (let i = 0; i < length; ++i) {
 			resultSet[array[i]] = true;
 		}
 	}
 
 	function _parse (resultSet, arg) {
 		if (!arg) return;
-		var argType = typeof arg;
+		const argType = typeof arg;
 
 		// 'foo bar'
 		if (argType === 'string') {
@@ -68,18 +68,18 @@ var classNames = (function () {
 	function _classNames () {
 		// don't leak arguments
 		// https://github.com/petkaantonov/bluebird/wiki/Optimization-killers#32-leaking-arguments
-		var len = arguments.length;
-		var args = Array(len);
-		for (var i = 0; i < len; i++) {
+		const length = arguments.length;
+		const args = Array(len);
+		for (const i = 0; i < length; i++) {
 			args[i] = arguments[i];
 		}
 
-		var classSet = new StorageObject();
+		const classSet = new StorageObject();
 		_parseArray(classSet, args);
 
-		var list = [];
+		const list = [];
 
-		for (var k in classSet) {
+		for (const k in classSet) {
 			if (classSet[k]) {
 				list.push(k)
 			}
diff --git a/index.js b/index.js
index ee6bbce..462992c 100644
--- a/index.js
+++ b/index.js
@@ -1,10 +1,10 @@
-var hasOwn = {}.hasOwnProperty;
+const hasOwn = {}.hasOwnProperty;
 
 export default function classNames () {
-	var classes = '';
+	let classes = '';
 
-	for (var i = 0; i < arguments.length; i++) {
-		var arg = arguments[i];
+	for (let i = 0; i < arguments.length; i++) {
+		const arg = arguments[i];
 		if (arg) {
 			classes = appendClass(classes, parseValue(arg));
 		}
@@ -30,9 +30,9 @@ function parseValue (arg) {
 		return arg.toString();
 	}
 
-	var classes = '';
+	let classes = '';
 
-	for (var key in arg) {
+	for (const key in arg) {
 		if (hasOwn.call(arg, key) && arg[key]) {
 			classes = appendClass(classes, key);
 		}