diff --git a/src/abortsignal-timeout.ts b/src/abortsignal-timeout.ts
deleted file mode 100644
index e9f6fac..0000000
--- a/src/abortsignal-timeout.ts
+++ /dev/null
@@ -1,27 +0,0 @@
-export function abortSignalTimeout(ms: number) {
-  const controller = new AbortController()
-  setTimeout(() => controller.abort(new DOMException('TimeoutError')), ms)
-  return controller.signal
-}
-
-declare global {
-  interface AbortController {
-    abort(reason: unknown): void
-  }
-}
-
-/*#__PURE__*/
-export function isSupported(): boolean {
-  return 'abort' in AbortSignal && typeof AbortSignal.timeout === 'function'
-}
-
-/*#__PURE__*/
-export function isPolyfilled(): boolean {
-  return AbortSignal.timeout === abortSignalTimeout
-}
-
-export function apply(): void {
-  if (!isSupported()) {
-    AbortSignal.timeout = abortSignalTimeout
-  }
-}
diff --git a/src/index.ts b/src/index.ts
index 53bb5b8..ac1003d 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,4 +1,3 @@
-import * as abortSignalTimeout from './abortsignal-timeout.js'
 import * as clipboardItem from './clipboarditem.js'
 import * as elementCheckVisibility from './element-checkvisibility.js'
 import * as navigatorClipboard from './navigator-clipboard.js'
@@ -30,7 +29,7 @@ export const baseSupport =
   'hasOwn' in Object &&
   // ESNext
   'abort' in AbortSignal &&
-  // 'timeout' in AbortSignal && // Polyfilled
+  'timeout' in AbortSignal &&
   // DOM / HTML and other specs
   typeof queueMicrotask === 'function' &&
   typeof HTMLDialogElement === 'function' &&
@@ -44,7 +43,6 @@ export const baseSupport =
   true
 
 export const polyfills = {
-  abortSignalTimeout,
   clipboardItem,
   elementCheckVisibility,
   navigatorClipboard,
diff --git a/test/abortsignal-timeout.js b/test/abortsignal-timeout.js
deleted file mode 100644
index a584bbb..0000000
--- a/test/abortsignal-timeout.js
+++ /dev/null
@@ -1,27 +0,0 @@
-import {abortSignalTimeout, apply, isPolyfilled, isSupported} from '../lib/abortsignal-timeout.js'
-
-describe('abortSignalTimeout', () => {
-  it('has standard isSupported, isPolyfilled, apply API', () => {
-    expect(isSupported).to.be.a('function')
-    expect(isPolyfilled).to.be.a('function')
-    expect(apply).to.be.a('function')
-    expect(isSupported()).to.be.a('boolean')
-    expect(isPolyfilled()).to.equal(false)
-  })
-
-  it('returns signal that will timeout', async () => {
-    expect(abortSignalTimeout()).to.be.instanceOf(AbortSignal)
-    const signal = abortSignalTimeout(0)
-    const longerSignal = abortSignalTimeout(20)
-    expect(signal.aborted).to.equal(false)
-    await new Promise(resolve => setTimeout(resolve, 10))
-    expect(signal.aborted).to.equal(true)
-    expect(longerSignal.aborted).to.equal(false)
-    await new Promise(resolve => setTimeout(resolve, 20))
-    expect(longerSignal.aborted).to.equal(true)
-  })
-
-  it('creates a new signal each time', () => {
-    expect(abortSignalTimeout()).to.not.equal(abortSignalTimeout())
-  })
-})