diff --git a/.travis.yml b/.travis.yml
index 58c605f..ba52fe3 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -6,9 +6,6 @@ os:
 language: node_js
 node_js:
   - node
-  - '11'
-  - '10'
-  - '9'
-  - '8'
-  - '7'
-  - '6'
+  - '16'
+  - '14'
+  - '12'
diff --git a/README.md b/README.md
index 5ac602a..78cfdd4 100644
--- a/README.md
+++ b/README.md
@@ -15,7 +15,8 @@ $ npm install --save union-value
 ## Usage
 
 ```js
-const union = require('union-value');
+import union from 'union-value';
+
 const obj = {};
 
 union(obj, 'a.b.c', ['one', 'two']);
@@ -70,10 +71,10 @@ You might also be interested in these projects:
 
 ### Contributors
 
-| **Commits** | **Contributor** |  
-| --- | --- |  
-| 23 | [jonschlinkert](https://github.com/jonschlinkert) |  
-| 1  | [wtgtybhertgeghgtwtg](https://github.com/wtgtybhertgeghgtwtg) |  
+| **Commits** | **Contributor** |
+| --- | --- |
+| 23 | [jonschlinkert](https://github.com/jonschlinkert) |
+| 1  | [wtgtybhertgeghgtwtg](https://github.com/wtgtybhertgeghgtwtg) |
 
 ### Author
 
@@ -90,4 +91,4 @@ Released under the [MIT License](LICENSE).
 
 ***
 
-_This file was generated by [verb-generate-readme](https://github.com/verbose/verb-generate-readme), v0.8.0, on June 20, 2019._
\ No newline at end of file
+_This file was generated by [verb-generate-readme](https://github.com/verbose/verb-generate-readme), v0.8.0, on June 20, 2019._
diff --git a/index.js b/index.js
index 1841d07..85fb4dd 100644
--- a/index.js
+++ b/index.js
@@ -1,26 +1,14 @@
-'use strict';
-
-const get = require('get-value');
-const set = require('set-value');
+import get from 'get-value';
+import set from 'set-value';
 
 const isObject = val => {
   return val != null && typeof val === 'object' && !Array.isArray(val);
 };
 
-const flatten = (...args) => {
-  let res = [];
-  let flat = arr => {
-    for (let ele of arr) Array.isArray(ele) ? flat(ele, res) : res.push(ele);
-  };
-  flat(args);
-  return res;
-};
-
-const unique = arr => arr.filter((v, i) => arr.indexOf(v) === i);
-const union = (...args) => unique(flatten(...args));
+const union = (...args) => [...new Set([...args].flat())];
 const first = (...args) => args.find(v => v != null);
 
-module.exports = (obj, prop, value) => {
+export default (obj, prop, value) => {
   if (!isObject(obj)) {
     throw new TypeError('expected the first argument to be an object');
   }
@@ -29,7 +17,7 @@ module.exports = (obj, prop, value) => {
     throw new TypeError('expected the second argument to be a string');
   }
 
-  let arr = [].concat(first(get(obj, prop), []));
+  const arr = [].concat(first(get(obj, prop), []));
   set(obj, prop, union(arr, [].concat(first(value, []))));
   return obj;
 };
diff --git a/package.json b/package.json
index e8b0df2..eb3dbf2 100644
--- a/package.json
+++ b/package.json
@@ -5,6 +5,7 @@
   "homepage": "https://github.com/jonschlinkert/union-value",
   "author": "Jon Schlinkert (https://github.com/jonschlinkert)",
   "repository": "jonschlinkert/union-value",
+  "type": "module",
   "bugs": {
     "url": "https://github.com/jonschlinkert/union-value/issues"
   },
@@ -14,15 +15,11 @@
   ],
   "main": "index.js",
   "engines": {
-    "node": ">=6"
+    "node": ">=12.20"
   },
   "scripts": {
     "test": "mocha"
   },
-  "dependencies": {
-    "get-value": "^3.0.1",
-    "set-value": "^3.0.0"
-  },
   "keywords": [
     "array",
     "dot",
@@ -60,8 +57,12 @@
       "reflinks": true
     }
   },
+  "dependencies": {
+    "get-value": "^3.0.1",
+    "set-value": "^4.1.0"
+  },
   "devDependencies": {
     "gulp-format-md": "^2.0.0",
-    "mocha": "^6.1.4"
+    "mocha": "^9.0.3"
   }
 }
diff --git a/test.js b/test.js
index 057ff48..3035638 100644
--- a/test.js
+++ b/test.js
@@ -1,38 +1,36 @@
-'use strict';
-
-require('mocha');
-const assert = require('assert');
-const union = require('./');
+import { deepEqual, throws } from 'node:assert';
+import 'mocha';
+import union from './index.js';
 
 describe('union', () => {
   it('should add a value:', () => {
     let obj = {};
     union(obj, 'foo', ['a', 'b'])
-    assert.deepEqual(obj.foo, ['a', 'b']);
+    deepEqual(obj.foo, ['a', 'b']);
   });
 
   it('should union a value:', () => {
     let obj = {foo: ['a', 'b']};
     union(obj, 'foo', ['c', 'd', 'e'])
-    assert.deepEqual(obj.foo, ['a', 'b', 'c', 'd', 'e']);
+    deepEqual(obj.foo, ['a', 'b', 'c', 'd', 'e']);
   });
 
   it('should union a deeply nested value:', () => {
     let obj = {};
     union(obj, 'a.b.c', ['one', 'two']);
     union(obj, 'a.b.c', ['three']);
-    assert.deepEqual(obj.a.b.c, ['one', 'two', 'three']);
+    deepEqual(obj.a.b.c, ['one', 'two', 'three']);
   });
 
   it('should support escaped dots:', () => {
     let obj = {};
     union(obj, 'a\\.b.c', ['one', 'two']);
     union(obj, 'a\\.b.c', ['three']);
-    assert.deepEqual(obj['a.b'].c, ['one', 'two', 'three']);
+    deepEqual(obj['a.b'].c, ['one', 'two', 'three']);
   });
 
   it('should throw an error:', () => {
-    assert.throws(() => union(), /expected the first argument to be an object/);
-    assert.throws(() => union({}), /expected the second argument to be a string/);
+    throws(() => union(), /expected the first argument to be an object/);
+    throws(() => union({}), /expected the second argument to be a string/);
   });
 });