diff --git a/index.js b/index.js
index 82593df..53bb2a6 100644
--- a/index.js
+++ b/index.js
@@ -1,10 +1,6 @@
-'use strict'
+import util from 'mdast-util-toc'
 
-var util = require('mdast-util-toc')
-
-module.exports = toc
-
-function toc(options = {}) {
+export default function remarkToc(options = {}) {
   return transformer
 
   function transformer(node) {
diff --git a/package.json b/package.json
index 5d8d212..2f14c56 100644
--- a/package.json
+++ b/package.json
@@ -33,9 +33,10 @@
     "Jonathan Haines <jonno.haines@gmail.com>",
     "Robin Millette <robin@millette.info>"
   ],
-  "types": "types/index.d.ts",
+  "sideEffects": false,
+  "type": "module",
+  "main": "index.js",
   "files": [
-    "types/index.d.ts",
     "index.js"
   ],
   "dependencies": {
diff --git a/test/index.js b/test/index.js
index af2c7dd..54a1b48 100644
--- a/test/index.js
+++ b/test/index.js
@@ -1,14 +1,12 @@
-'use strict'
-
-var fs = require('fs')
-var path = require('path')
-var test = require('tape')
-var remark = require('remark')
-var hidden = require('is-hidden')
-var toc = require('..')
+import fs from 'fs'
+import path from 'path'
+import test from 'tape'
+import remark from 'remark'
+import hidden from 'is-hidden'
+import toc from '../index.js'
 
 test('Fixtures', function (t) {
-  var root = path.join(__dirname, 'fixtures')
+  var root = path.join('test', 'fixtures')
   var fixtures = fs.readdirSync(root)
   var index = -1
   var fixture