diff --git a/lib/index.js b/lib/index.js
index c7cf688..69e22e9 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -1,3 +1,6 @@
+/// <reference types="remark-parse" />
+/// <reference types="remark-stringify" />
+
 /**
  * @typedef {import('mdast').Root} Root
  * @typedef {import('micromark-extension-frontmatter').Options} Options
@@ -32,24 +35,14 @@ export default function remarkFrontmatter(options) {
   const settings = options || emptyOptions
   const data = self.data()
 
-  add('micromarkExtensions', frontmatter(settings))
-  add('fromMarkdownExtensions', frontmatterFromMarkdown(settings))
-  add('toMarkdownExtensions', frontmatterToMarkdown(settings))
-
-  /**
-   * @param {string} field
-   * @param {unknown} value
-   */
-  function add(field, value) {
-    // Other extensions
-    // @ts-expect-error: to do: remove when remark is released.
-    let list = /** @type {Array<unknown>} */ (data[field])
-    if (!list) {
-      list = []
-      // @ts-expect-error: to do: remove when remark is released.
-      data[field] = list
-    }
+  const micromarkExtensions =
+    data.micromarkExtensions || (data.micromarkExtensions = [])
+  const fromMarkdownExtensions =
+    data.fromMarkdownExtensions || (data.fromMarkdownExtensions = [])
+  const toMarkdownExtensions =
+    data.toMarkdownExtensions || (data.toMarkdownExtensions = [])
 
-    list.push(value)
-  }
+  micromarkExtensions.push(frontmatter(settings))
+  fromMarkdownExtensions.push(frontmatterFromMarkdown(settings))
+  toMarkdownExtensions.push(frontmatterToMarkdown(settings))
 }
diff --git a/package.json b/package.json
index 278cd56..965e09d 100644
--- a/package.json
+++ b/package.json
@@ -46,7 +46,7 @@
     "c8": "^8.0.0",
     "is-hidden": "^2.0.0",
     "prettier": "^3.0.0",
-    "remark": "^14.0.0",
+    "remark": "^15.0.0",
     "remark-cli": "^11.0.0",
     "remark-preset-wooorm": "^9.0.0",
     "type-coverage": "^2.0.0",
diff --git a/test/index.js b/test/index.js
index b246a14..0c2f482 100644
--- a/test/index.js
+++ b/test/index.js
@@ -9,7 +9,6 @@ import process from 'node:process'
 import test from 'node:test'
 import {isHidden} from 'is-hidden'
 import {remark} from 'remark'
-import {unified} from 'unified'
 import remarkFrontmatter from '../index.js'
 
 test('remarkFrontmatter', async function (t) {
@@ -25,21 +24,12 @@ test('remarkFrontmatter', async function (t) {
     })
   })
 
-  await t.test(
-    'should not throw if without parser or compiler',
-    async function () {
-      assert.doesNotThrow(function () {
-        unified().use(remarkFrontmatter).freeze()
-      })
-    }
-  )
-
   await t.test(
     'should throw if not given a preset or a matter',
     async function () {
       assert.throws(function () {
         // @ts-expect-error: check how invalid input is handled.
-        unified().use(remarkFrontmatter, [1]).freeze()
+        remark().use(remarkFrontmatter, [1]).freeze()
       }, /^Error: Expected matter to be an object, not `1`/)
     }
   )
@@ -47,7 +37,7 @@ test('remarkFrontmatter', async function (t) {
   await t.test('should throw if given an unknown preset', async function () {
     assert.throws(function () {
       // @ts-expect-error: check how invalid input is handled.
-      unified().use(remarkFrontmatter, ['jsonml']).freeze()
+      remark().use(remarkFrontmatter, ['jsonml']).freeze()
     }, /^Error: Missing matter definition for `jsonml`/)
   })
 
@@ -55,7 +45,7 @@ test('remarkFrontmatter', async function (t) {
     'should throw if given a matter without `type`',
     async function () {
       assert.throws(function () {
-        unified()
+        remark()
           // @ts-expect-error: check how invalid input is handled.
           .use(remarkFrontmatter, [{marker: '*'}])
           .freeze()
@@ -67,7 +57,7 @@ test('remarkFrontmatter', async function (t) {
     'should throw if given a matter without `marker`',
     async function () {
       assert.throws(function () {
-        unified()
+        remark()
           // @ts-expect-error: check how invalid input is handled.
           .use(remarkFrontmatter, [{type: 'jsonml'}])
           .freeze()
@@ -108,8 +98,6 @@ test('fixtures', async function (t) {
       } catch {}
 
       const proc = remark().use(remarkFrontmatter, config)
-      /** @type {Root} */
-      // @ts-expect-error: remove when remark is released.
       const actual = proc.parse(input)
 
       try {