diff --git a/README.md b/README.md
index 1e0b5c98..4d4e9b27 100644
--- a/README.md
+++ b/README.md
@@ -79,13 +79,17 @@ Options:
 
 - `filter` Method that receives a path string as an argument, and
   returns a boolean indicating whether that path should be
-  deleted.
-
-  If a filter method is provided, it _must_ return a truthy
-  value, or nothing will be removed. Filtering out a directory
-  will still allow its children to be removed, unless they are
-  also filtered out, but any parents of a filtered entry will not
-  be removed.
+  deleted.  With async rimraf methods, this may return a Promise
+  that resolves to a boolean.  (Since Promises are truthy,
+  returning a Promise from a sync filter is the same as just not
+  filtering anything.)
+
+  If a filter method is provided, it will _only_ remove entries
+  if the filter returns (or resolves to) a truthy value. Omitting
+  a directory will still allow its children to be removed, unless
+  they are also filtered out, but any parents of a filtered entry
+  will not be removed, since the directory would not be empty in
+  that case.
 
   Using a filter method prevents the use of Node's built-in
   `fs.rm` because that implementation does not support filtering.
diff --git a/src/index.ts b/src/index.ts
index 7d845f18..3c5443ca 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,9 +1,9 @@
-import optArg from './opt-arg.js'
+import { optArg, optArgSync } from './opt-arg.js'
 import pathArg from './path-arg.js'
 
 import { glob, GlobOptions, globSync } from 'glob'
 
-export interface RimrafOptions {
+export interface RimrafAsyncOptions {
   preserveRoot?: boolean
   tmp?: string
   maxRetries?: number
@@ -12,9 +12,15 @@ export interface RimrafOptions {
   maxBackoff?: number
   signal?: AbortSignal
   glob?: boolean | GlobOptions
+  filter?: ((path: string) => boolean) | ((path: string) => Promise<boolean>)
+}
+
+export interface RimrafSyncOptions extends RimrafAsyncOptions {
   filter?: (path: string) => boolean
 }
 
+export type RimrafOptions = RimrafSyncOptions | RimrafAsyncOptions
+
 const typeOrUndef = (val: any, t: string) =>
   typeof val === 'undefined' || typeof val === t
 
@@ -46,8 +52,11 @@ import { rimrafWindows, rimrafWindowsSync } from './rimraf-windows.js'
 import { useNative, useNativeSync } from './use-native.js'
 
 const wrap =
-  (fn: (p: string, o: RimrafOptions) => Promise<boolean>) =>
-  async (path: string | string[], opt?: RimrafOptions): Promise<boolean> => {
+  (fn: (p: string, o: RimrafAsyncOptions) => Promise<boolean>) =>
+  async (
+    path: string | string[],
+    opt?: RimrafAsyncOptions
+  ): Promise<boolean> => {
     const options = optArg(opt)
     if (options.glob) {
       path = await glob(path, options.glob)
@@ -62,9 +71,9 @@ const wrap =
   }
 
 const wrapSync =
-  (fn: (p: string, o: RimrafOptions) => boolean) =>
-  (path: string | string[], opt?: RimrafOptions): boolean => {
-    const options = optArg(opt)
+  (fn: (p: string, o: RimrafSyncOptions) => boolean) =>
+  (path: string | string[], opt?: RimrafSyncOptions): boolean => {
+    const options = optArgSync(opt)
     if (options.glob) {
       path = globSync(path, options.glob)
     }
diff --git a/src/opt-arg.ts b/src/opt-arg.ts
index b2f7e61a..a9473c51 100644
--- a/src/opt-arg.ts
+++ b/src/opt-arg.ts
@@ -1,13 +1,23 @@
 import { GlobOptions } from 'glob'
-import { assertRimrafOptions, RimrafOptions } from './index.js'
-export default (
-  opt: RimrafOptions = {}
-): RimrafOptions & {
-  glob?: GlobOptions & { withFileTypes: false }
-} => {
+import {
+  assertRimrafOptions,
+  RimrafAsyncOptions,
+  RimrafOptions,
+  RimrafSyncOptions,
+} from './index.js'
+
+const optArgT = <T extends RimrafOptions>(
+  opt: T
+):
+  | (T & {
+      glob: GlobOptions & { withFileTypes: false }
+    })
+  | (T & { glob: undefined }) => {
   assertRimrafOptions(opt)
   const { glob, ...options } = opt
-  if (!glob) return options
+  if (!glob) {
+    return options as T & { glob: undefined }
+  }
   const globOpt =
     glob === true
       ? opt.signal
@@ -28,5 +38,8 @@ export default (
       absolute: true,
       withFileTypes: false,
     },
-  }
+  } as T & { glob: GlobOptions & { withFileTypes: false } }
 }
+
+export const optArg = (opt: RimrafAsyncOptions = {}) => optArgT(opt)
+export const optArgSync = (opt: RimrafSyncOptions = {}) => optArgT(opt)
diff --git a/src/path-arg.ts b/src/path-arg.ts
index 4adaf5e8..68ca4403 100644
--- a/src/path-arg.ts
+++ b/src/path-arg.ts
@@ -1,9 +1,9 @@
-import platform from './platform.js'
-import { resolve, parse } from 'path'
+import { parse, resolve } from 'path'
 import { inspect } from 'util'
-import { RimrafOptions } from './index.js'
+import { RimrafAsyncOptions } from './index.js'
+import platform from './platform.js'
 
-const pathArg = (path: string, opt: RimrafOptions = {}) => {
+const pathArg = (path: string, opt: RimrafAsyncOptions = {}) => {
   const type = typeof path
   if (type !== 'string') {
     const ctor = path && type === 'object' && path.constructor
diff --git a/src/retry-busy.ts b/src/retry-busy.ts
index 5f2eb3c6..0c09890f 100644
--- a/src/retry-busy.ts
+++ b/src/retry-busy.ts
@@ -1,6 +1,6 @@
 // note: max backoff is the maximum that any *single* backoff will do
 
-import { RimrafOptions } from '.'
+import { RimrafAsyncOptions, RimrafOptions } from '.'
 
 export const MAXBACKOFF = 200
 export const RATE = 1.2
@@ -10,7 +10,7 @@ export const codes = new Set(['EMFILE', 'ENFILE', 'EBUSY'])
 export const retryBusy = (fn: (path: string) => Promise<any>) => {
   const method = async (
     path: string,
-    opt: RimrafOptions,
+    opt: RimrafAsyncOptions,
     backoff = 1,
     total = 0
   ) => {
diff --git a/src/rimraf-move-remove.ts b/src/rimraf-move-remove.ts
index a28262ed..2cac797b 100644
--- a/src/rimraf-move-remove.ts
+++ b/src/rimraf-move-remove.ts
@@ -25,7 +25,7 @@ import {
 } from './fs.js'
 const { rename, unlink, rmdir, chmod } = fsPromises
 
-import { RimrafOptions } from '.'
+import { RimrafAsyncOptions, RimrafSyncOptions } from '.'
 import { readdirOrError, readdirOrErrorSync } from './readdir-or-error.js'
 
 // crypto.randomBytes is much slower, and Math.random() is enough here
@@ -71,7 +71,7 @@ const unlinkFixEPERMSync = (path: string) => {
 
 export const rimrafMoveRemove = async (
   path: string,
-  opt: RimrafOptions
+  opt: RimrafAsyncOptions
 ): Promise<boolean> => {
   if (opt?.signal?.aborted) {
     throw opt.signal.reason
@@ -91,7 +91,7 @@ export const rimrafMoveRemove = async (
     if (entries.code !== 'ENOTDIR') {
       throw entries
     }
-    if (opt.filter && !opt.filter(path)) {
+    if (opt.filter && !(await opt.filter(path))) {
       return false
     }
     await ignoreENOENT(tmpUnlink(path, opt.tmp, unlinkFixEPERM))
@@ -113,7 +113,7 @@ export const rimrafMoveRemove = async (
   if (opt.preserveRoot === false && path === parse(path).root) {
     return false
   }
-  if (opt.filter && !opt.filter(path)) {
+  if (opt.filter && !(await opt.filter(path))) {
     return false
   }
   await ignoreENOENT(tmpUnlink(path, opt.tmp, rmdir))
@@ -132,7 +132,7 @@ const tmpUnlink = async (
 
 export const rimrafMoveRemoveSync = (
   path: string,
-  opt: RimrafOptions
+  opt: RimrafSyncOptions
 ): boolean => {
   if (opt?.signal?.aborted) {
     throw opt.signal.reason
diff --git a/src/rimraf-native.ts b/src/rimraf-native.ts
index 47e2bc34..4e793943 100644
--- a/src/rimraf-native.ts
+++ b/src/rimraf-native.ts
@@ -1,10 +1,10 @@
-import { RimrafOptions } from '.'
+import { RimrafAsyncOptions, RimrafSyncOptions } from '.'
 import { promises, rmSync } from './fs.js'
 const { rm } = promises
 
 export const rimrafNative = async (
   path: string,
-  opt: RimrafOptions
+  opt: RimrafAsyncOptions
 ): Promise<boolean> => {
   await rm(path, {
     ...opt,
@@ -14,7 +14,10 @@ export const rimrafNative = async (
   return true
 }
 
-export const rimrafNativeSync = (path: string, opt: RimrafOptions): boolean => {
+export const rimrafNativeSync = (
+  path: string,
+  opt: RimrafSyncOptions
+): boolean => {
   rmSync(path, {
     ...opt,
     force: true,
diff --git a/src/rimraf-posix.ts b/src/rimraf-posix.ts
index 6fa79e2e..a4a4c69a 100644
--- a/src/rimraf-posix.ts
+++ b/src/rimraf-posix.ts
@@ -12,12 +12,12 @@ import { parse, resolve } from 'path'
 
 import { readdirOrError, readdirOrErrorSync } from './readdir-or-error.js'
 
-import { RimrafOptions } from '.'
+import { RimrafAsyncOptions, RimrafSyncOptions } from '.'
 import { ignoreENOENT, ignoreENOENTSync } from './ignore-enoent.js'
 
 export const rimrafPosix = async (
   path: string,
-  opt: RimrafOptions
+  opt: RimrafAsyncOptions
 ): Promise<boolean> => {
   if (opt?.signal?.aborted) {
     throw opt.signal.reason
@@ -30,7 +30,7 @@ export const rimrafPosix = async (
     if (entries.code !== 'ENOTDIR') {
       throw entries
     }
-    if (opt.filter && !opt.filter(path)) {
+    if (opt.filter && !(await opt.filter(path))) {
       return false
     }
     await ignoreENOENT(unlink(path))
@@ -54,7 +54,7 @@ export const rimrafPosix = async (
     return false
   }
 
-  if (opt.filter && !opt.filter(path)) {
+  if (opt.filter && !(await opt.filter(path))) {
     return false
   }
 
@@ -62,7 +62,10 @@ export const rimrafPosix = async (
   return true
 }
 
-export const rimrafPosixSync = (path: string, opt: RimrafOptions): boolean => {
+export const rimrafPosixSync = (
+  path: string,
+  opt: RimrafSyncOptions
+): boolean => {
   if (opt?.signal?.aborted) {
     throw opt.signal.reason
   }
@@ -84,11 +87,11 @@ export const rimrafPosixSync = (path: string, opt: RimrafOptions): boolean => {
   for (const entry of entries) {
     removedAll = rimrafPosixSync(resolve(path, entry), opt) && removedAll
   }
-  if (!removedAll) {
+  if (opt.preserveRoot === false && path === parse(path).root) {
     return false
   }
 
-  if (opt.preserveRoot === false && path === parse(path).root) {
+  if (!removedAll) {
     return false
   }
 
diff --git a/src/rimraf-windows.ts b/src/rimraf-windows.ts
index 68728f08..8582a1b5 100644
--- a/src/rimraf-windows.ts
+++ b/src/rimraf-windows.ts
@@ -9,7 +9,7 @@
 // Note: "move then remove" is 2-10 times slower, and just as unreliable.
 
 import { parse, resolve } from 'path'
-import { RimrafOptions } from '.'
+import { RimrafAsyncOptions, RimrafSyncOptions } from '.'
 import { fixEPERM, fixEPERMSync } from './fix-eperm.js'
 import { promises, rmdirSync, unlinkSync } from './fs.js'
 import { ignoreENOENT, ignoreENOENTSync } from './ignore-enoent.js'
@@ -25,7 +25,7 @@ const rimrafWindowsDirSync = retryBusySync(fixEPERMSync(rmdirSync))
 
 const rimrafWindowsDirMoveRemoveFallback = async (
   path: string,
-  opt: RimrafOptions
+  opt: RimrafAsyncOptions
 ): Promise<boolean> => {
   /* c8 ignore start */
   if (opt?.signal?.aborted) {
@@ -46,7 +46,7 @@ const rimrafWindowsDirMoveRemoveFallback = async (
 
 const rimrafWindowsDirMoveRemoveFallbackSync = (
   path: string,
-  opt: RimrafOptions
+  opt: RimrafSyncOptions
 ): boolean => {
   if (opt?.signal?.aborted) {
     throw opt.signal.reason
@@ -71,7 +71,7 @@ const states = new Set([START, CHILD, FINISH])
 
 export const rimrafWindows = async (
   path: string,
-  opt: RimrafOptions,
+  opt: RimrafAsyncOptions,
   state = START
 ): Promise<boolean> => {
   if (opt?.signal?.aborted) {
@@ -89,7 +89,7 @@ export const rimrafWindows = async (
     if (entries.code !== 'ENOTDIR') {
       throw entries
     }
-    if (opt.filter && !opt.filter(path)) {
+    if (opt.filter && !(await opt.filter(path))) {
       return false
     }
     // is a file
@@ -110,10 +110,10 @@ export const rimrafWindows = async (
     if (opt.preserveRoot === false && path === parse(path).root) {
       return false
     }
-    if (opt.filter && !opt.filter(path)) {
+    if (!removedAll) {
       return false
     }
-    if (!removedAll) {
+    if (opt.filter && !(await opt.filter(path))) {
       return false
     }
     await ignoreENOENT(rimrafWindowsDirMoveRemoveFallback(path, opt))
@@ -123,7 +123,7 @@ export const rimrafWindows = async (
 
 export const rimrafWindowsSync = (
   path: string,
-  opt: RimrafOptions,
+  opt: RimrafSyncOptions,
   state = START
 ): boolean => {
   if (!states.has(state)) {
@@ -158,10 +158,10 @@ export const rimrafWindowsSync = (
     if (opt.preserveRoot === false && path === parse(path).root) {
       return false
     }
-    if (opt.filter && !opt.filter(path)) {
+    if (!removedAll) {
       return false
     }
-    if (!removedAll) {
+    if (opt.filter && !opt.filter(path)) {
       return false
     }
     ignoreENOENTSync(() => {
diff --git a/src/use-native.ts b/src/use-native.ts
index 76f47e55..915784e3 100644
--- a/src/use-native.ts
+++ b/src/use-native.ts
@@ -1,11 +1,11 @@
 const version = process.env.__TESTING_RIMRAF_NODE_VERSION__ || process.version
 const versArr = version.replace(/^v/, '').split('.')
 const hasNative = +versArr[0] > 14 || (+versArr[0] === 14 && +versArr[1] >= 14)
-import { RimrafOptions } from './index.js'
+import { RimrafAsyncOptions, RimrafOptions } from './index.js'
 // we do NOT use native by default on Windows, because Node's native
 // rm implementation is less advanced.  Change this code if that changes.
 import platform from './platform.js'
-export const useNative: (opt?: RimrafOptions) => boolean =
+export const useNative: (opt?: RimrafAsyncOptions) => boolean =
   !hasNative || platform === 'win32'
     ? () => false
     : opt => !opt?.signal && !opt?.filter
diff --git a/tap-snapshots/test/rimraf-move-remove.js.test.cjs b/tap-snapshots/test/rimraf-move-remove.js.test.cjs
index c6e8d882..def1c0c4 100644
--- a/tap-snapshots/test/rimraf-move-remove.js.test.cjs
+++ b/tap-snapshots/test/rimraf-move-remove.js.test.cjs
@@ -23,6 +23,24 @@ Array [
 ]
 `
 
+exports[`test/rimraf-move-remove.js TAP filter function filter=i async filter > paths seen 1`] = `
+Array [
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-i-async-filter/a",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-i-async-filter/b",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-i-async-filter/c/d",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-i-async-filter/c/e",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-i-async-filter/c/f/g",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-i-async-filter/c/f/h",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-i-async-filter/c/f/i",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-i-async-filter/c/f/i/j",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-i-async-filter/c/f/i/k",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-i-async-filter/c/f/i/l",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-i-async-filter/c/f/i/m",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-i-async-filter/c/f/i/m/n",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-i-async-filter/c/f/i/m/o",
+]
+`
+
 exports[`test/rimraf-move-remove.js TAP filter function filter=i sync > paths seen 1`] = `
 Array [
   "test/tap-testdir-rimraf-move-remove-filter-function-filter-i-sync/a",
@@ -58,6 +76,23 @@ Array [
 ]
 `
 
+exports[`test/rimraf-move-remove.js TAP filter function filter=j async filter > paths seen 1`] = `
+Array [
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-j-async-filter/a",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-j-async-filter/b",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-j-async-filter/c/d",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-j-async-filter/c/e",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-j-async-filter/c/f/g",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-j-async-filter/c/f/h",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-j-async-filter/c/f/i/j",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-j-async-filter/c/f/i/k",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-j-async-filter/c/f/i/l",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-j-async-filter/c/f/i/m",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-j-async-filter/c/f/i/m/n",
+  "test/tap-testdir-rimraf-move-remove-filter-function-filter-j-async-filter/c/f/i/m/o",
+]
+`
+
 exports[`test/rimraf-move-remove.js TAP filter function filter=j sync > paths seen 1`] = `
 Array [
   "test/tap-testdir-rimraf-move-remove-filter-function-filter-j-sync/a",
diff --git a/tap-snapshots/test/rimraf-posix.js.test.cjs b/tap-snapshots/test/rimraf-posix.js.test.cjs
index 93ae5152..97c449bb 100644
--- a/tap-snapshots/test/rimraf-posix.js.test.cjs
+++ b/tap-snapshots/test/rimraf-posix.js.test.cjs
@@ -23,6 +23,24 @@ Array [
 ]
 `
 
+exports[`test/rimraf-posix.js TAP filter function filter=i async filter > paths seen 1`] = `
+Array [
+  "test/tap-testdir-rimraf-posix-filter-function-filter-i-async-filter/a",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-i-async-filter/b",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-i-async-filter/c/d",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-i-async-filter/c/e",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-i-async-filter/c/f/g",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-i-async-filter/c/f/h",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-i-async-filter/c/f/i",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-i-async-filter/c/f/i/j",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-i-async-filter/c/f/i/k",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-i-async-filter/c/f/i/l",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-i-async-filter/c/f/i/m",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-i-async-filter/c/f/i/m/n",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-i-async-filter/c/f/i/m/o",
+]
+`
+
 exports[`test/rimraf-posix.js TAP filter function filter=i sync > paths seen 1`] = `
 Array [
   "test/tap-testdir-rimraf-posix-filter-function-filter-i-sync/a",
@@ -58,6 +76,23 @@ Array [
 ]
 `
 
+exports[`test/rimraf-posix.js TAP filter function filter=j async filter > paths seen 1`] = `
+Array [
+  "test/tap-testdir-rimraf-posix-filter-function-filter-j-async-filter/a",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-j-async-filter/b",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-j-async-filter/c/d",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-j-async-filter/c/e",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-j-async-filter/c/f/g",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-j-async-filter/c/f/h",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-j-async-filter/c/f/i/j",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-j-async-filter/c/f/i/k",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-j-async-filter/c/f/i/l",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-j-async-filter/c/f/i/m",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-j-async-filter/c/f/i/m/n",
+  "test/tap-testdir-rimraf-posix-filter-function-filter-j-async-filter/c/f/i/m/o",
+]
+`
+
 exports[`test/rimraf-posix.js TAP filter function filter=j sync > paths seen 1`] = `
 Array [
   "test/tap-testdir-rimraf-posix-filter-function-filter-j-sync/a",
diff --git a/tap-snapshots/test/rimraf-windows.js.test.cjs b/tap-snapshots/test/rimraf-windows.js.test.cjs
index 3c85c6c0..92cd6a42 100644
--- a/tap-snapshots/test/rimraf-windows.js.test.cjs
+++ b/tap-snapshots/test/rimraf-windows.js.test.cjs
@@ -7,13 +7,10 @@
 'use strict'
 exports[`test/rimraf-windows.js TAP filter function filter=i async > paths seen 1`] = `
 Array [
-  "test/tap-testdir-rimraf-windows-filter-function-filter-i-async",
   "test/tap-testdir-rimraf-windows-filter-function-filter-i-async/a",
   "test/tap-testdir-rimraf-windows-filter-function-filter-i-async/b",
-  "test/tap-testdir-rimraf-windows-filter-function-filter-i-async/c",
   "test/tap-testdir-rimraf-windows-filter-function-filter-i-async/c/d",
   "test/tap-testdir-rimraf-windows-filter-function-filter-i-async/c/e",
-  "test/tap-testdir-rimraf-windows-filter-function-filter-i-async/c/f",
   "test/tap-testdir-rimraf-windows-filter-function-filter-i-async/c/f/g",
   "test/tap-testdir-rimraf-windows-filter-function-filter-i-async/c/f/h",
   "test/tap-testdir-rimraf-windows-filter-function-filter-i-async/c/f/i",
@@ -26,15 +23,30 @@ Array [
 ]
 `
 
+exports[`test/rimraf-windows.js TAP filter function filter=i async filter > paths seen 1`] = `
+Array [
+  "test/tap-testdir-rimraf-windows-filter-function-filter-i-async-filter/a",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-i-async-filter/b",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-i-async-filter/c/d",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-i-async-filter/c/e",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-i-async-filter/c/f/g",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-i-async-filter/c/f/h",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-i-async-filter/c/f/i",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-i-async-filter/c/f/i/j",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-i-async-filter/c/f/i/k",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-i-async-filter/c/f/i/l",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-i-async-filter/c/f/i/m",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-i-async-filter/c/f/i/m/n",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-i-async-filter/c/f/i/m/o",
+]
+`
+
 exports[`test/rimraf-windows.js TAP filter function filter=i sync > paths seen 1`] = `
 Array [
-  "test/tap-testdir-rimraf-windows-filter-function-filter-i-sync",
   "test/tap-testdir-rimraf-windows-filter-function-filter-i-sync/a",
   "test/tap-testdir-rimraf-windows-filter-function-filter-i-sync/b",
-  "test/tap-testdir-rimraf-windows-filter-function-filter-i-sync/c",
   "test/tap-testdir-rimraf-windows-filter-function-filter-i-sync/c/d",
   "test/tap-testdir-rimraf-windows-filter-function-filter-i-sync/c/e",
-  "test/tap-testdir-rimraf-windows-filter-function-filter-i-sync/c/f",
   "test/tap-testdir-rimraf-windows-filter-function-filter-i-sync/c/f/g",
   "test/tap-testdir-rimraf-windows-filter-function-filter-i-sync/c/f/h",
   "test/tap-testdir-rimraf-windows-filter-function-filter-i-sync/c/f/i",
@@ -49,16 +61,12 @@ Array [
 
 exports[`test/rimraf-windows.js TAP filter function filter=j async > paths seen 1`] = `
 Array [
-  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-async/a",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-async/b",
-  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async/c",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-async/c/d",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-async/c/e",
-  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async/c/f",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-async/c/f/g",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-async/c/f/h",
-  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async/c/f/i",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-async/c/f/i/j",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-async/c/f/i/j",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-async/c/f/i/k",
@@ -69,18 +77,32 @@ Array [
 ]
 `
 
+exports[`test/rimraf-windows.js TAP filter function filter=j async filter > paths seen 1`] = `
+Array [
+  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async-filter/a",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async-filter/b",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async-filter/c/d",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async-filter/c/e",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async-filter/c/f/g",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async-filter/c/f/h",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async-filter/c/f/i/j",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async-filter/c/f/i/j",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async-filter/c/f/i/k",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async-filter/c/f/i/l",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async-filter/c/f/i/m",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async-filter/c/f/i/m/n",
+  "test/tap-testdir-rimraf-windows-filter-function-filter-j-async-filter/c/f/i/m/o",
+]
+`
+
 exports[`test/rimraf-windows.js TAP filter function filter=j sync > paths seen 1`] = `
 Array [
-  "test/tap-testdir-rimraf-windows-filter-function-filter-j-sync",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-sync/a",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-sync/b",
-  "test/tap-testdir-rimraf-windows-filter-function-filter-j-sync/c",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-sync/c/d",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-sync/c/e",
-  "test/tap-testdir-rimraf-windows-filter-function-filter-j-sync/c/f",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-sync/c/f/g",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-sync/c/f/h",
-  "test/tap-testdir-rimraf-windows-filter-function-filter-j-sync/c/f/i",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-sync/c/f/i/j",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-sync/c/f/i/j",
   "test/tap-testdir-rimraf-windows-filter-function-filter-j-sync/c/f/i/k",
diff --git a/test/index.js b/test/index.js
index ddac1778..ca23438f 100644
--- a/test/index.js
+++ b/test/index.js
@@ -37,9 +37,15 @@ t.test('mocky unit tests to select the correct function', t => {
       CALLS.push(['pathArg', path])
       return path
     },
-    '../dist/cjs/src/opt-arg.js': opt => {
-      CALLS.push(['optArg', opt])
-      return opt
+    '../dist/cjs/src/opt-arg.js': {
+      optArg: opt => {
+        CALLS.push(['optArg', opt])
+        return opt
+      },
+      optArgSync: opt => {
+        CALLS.push(['optArg', opt])
+        return opt
+      },
     },
     '../dist/cjs/src/rimraf-posix.js': {
       rimrafPosix: async (path, opt) => {
diff --git a/test/opt-arg.js b/test/opt-arg.js
index 13880255..fc08e367 100644
--- a/test/opt-arg.js
+++ b/test/opt-arg.js
@@ -1,13 +1,15 @@
 const t = require('tap')
-const optArg = require('../dist/cjs/src/opt-arg.js').default
+const { optArg: oa, optArgSync: oas } = require('../dist/cjs/src/opt-arg.js')
 const opt = { a: 1 }
-t.same(optArg(opt), opt, 'returns equivalent object if provided')
-t.same(optArg(), {}, 'returns new object otherwise')
 
-t.throws(() => optArg(true))
-t.throws(() => optArg(null))
-t.throws(() => optArg('hello'))
-t.throws(() => optArg({ maxRetries: 'banana' }))
+t.same(oa(opt), opt, 'returns equivalent object if provided')
+t.same(oas(opt), oa(opt), 'optArgSync does the same thing')
+t.same(oa(), {}, 'returns new object otherwise')
+
+t.throws(() => oa(true))
+t.throws(() => oa(null))
+t.throws(() => oa('hello'))
+t.throws(() => oa({ maxRetries: 'banana' }))
 
 t.test('every kind of invalid option value', t => {
   // skip them when it's undefined, and skip the case
@@ -33,7 +35,7 @@ t.test('every kind of invalid option value', t => {
                 continue
               }
               t.throws(() =>
-                optArg({
+                oa({
                   preserveRoot,
                   maxRetries,
                   retryDelay,
@@ -64,7 +66,7 @@ t.test('test every allowed combination', t => {
           for (const backoff of goodNum) {
             for (const maxBackoff of goodNum) {
               t.ok(
-                optArg({
+                oa({
                   preserveRoot,
                   maxRetries,
                   retryDelay,
@@ -83,19 +85,19 @@ t.test('test every allowed combination', t => {
 })
 
 t.test('glob option handling', t => {
-  t.same(optArg({ glob: true }), {
+  t.same(oa({ glob: true }), {
     glob: { absolute: true, withFileTypes: false },
   })
-  const gws = optArg({ signal: { x: 1 }, glob: true })
+  const gws = oa({ signal: { x: 1 }, glob: true })
   t.same(gws, {
     signal: { x: 1 },
     glob: { absolute: true, signal: { x: 1 }, withFileTypes: false },
   })
   t.equal(gws.signal, gws.glob.signal)
-  t.same(optArg({ glob: { nodir: true } }), {
+  t.same(oa({ glob: { nodir: true } }), {
     glob: { absolute: true, nodir: true, withFileTypes: false },
   })
-  const gwsg = optArg({ signal: { x: 1 }, glob: { nodir: true } })
+  const gwsg = oa({ signal: { x: 1 }, glob: { nodir: true } })
   t.same(gwsg, {
     signal: { x: 1 },
     glob: {
@@ -106,17 +108,14 @@ t.test('glob option handling', t => {
     },
   })
   t.equal(gwsg.signal, gwsg.glob.signal)
-  t.same(
-    optArg({ signal: { x: 1 }, glob: { nodir: true, signal: { y: 1 } } }),
-    {
-      signal: { x: 1 },
-      glob: {
-        absolute: true,
-        nodir: true,
-        signal: { y: 1 },
-        withFileTypes: false,
-      },
-    }
-  )
+  t.same(oa({ signal: { x: 1 }, glob: { nodir: true, signal: { y: 1 } } }), {
+    signal: { x: 1 },
+    glob: {
+      absolute: true,
+      nodir: true,
+      signal: { y: 1 },
+      withFileTypes: false,
+    },
+  })
   t.end()
 })
diff --git a/test/rimraf-move-remove.js b/test/rimraf-move-remove.js
index 9ce9e982..1c98e56e 100644
--- a/test/rimraf-move-remove.js
+++ b/test/rimraf-move-remove.js
@@ -612,6 +612,39 @@ t.test('filter function', t => {
         t.throws(() => statSync(dir + '/c/f/i/l'))
         t.throws(() => statSync(dir + '/c/f/i/m'))
       })
+
+      t.test('async filter', async t => {
+        const dir = t.testdir(fixture)
+        const saw = []
+        const filter = async p => {
+          saw.push(relative(process.cwd(), p).replace(/\\/g, '/'))
+          await new Promise(setImmediate)
+          return basename(p) !== f
+        }
+        await rimrafMoveRemove(dir, { filter })
+        t.matchSnapshot(
+          saw.sort((a, b) => a.localeCompare(b, 'en')),
+          'paths seen'
+        )
+        statSync(dir)
+        statSync(dir + '/c')
+        statSync(dir + '/c/f')
+        statSync(dir + '/c/f/i')
+        if (f === 'j') {
+          statSync(dir + '/c/f/i/j')
+        } else {
+          t.throws(() => statSync(dir + '/c/f/i/j'))
+        }
+        t.throws(() => statSync(dir + '/a'))
+        t.throws(() => statSync(dir + '/b'))
+        t.throws(() => statSync(dir + '/c/d'))
+        t.throws(() => statSync(dir + '/c/e'))
+        t.throws(() => statSync(dir + '/c/f/g'))
+        t.throws(() => statSync(dir + '/c/f/h'))
+        t.throws(() => statSync(dir + '/c/f/i/k'))
+        t.throws(() => statSync(dir + '/c/f/i/l'))
+        t.throws(() => statSync(dir + '/c/f/i/m'))
+      })
       t.end()
     })
   }
diff --git a/test/rimraf-posix.js b/test/rimraf-posix.js
index e5ce11eb..7c7e0b28 100644
--- a/test/rimraf-posix.js
+++ b/test/rimraf-posix.js
@@ -308,6 +308,39 @@ t.test('filter function', t => {
         t.throws(() => statSync(dir + '/c/f/i/l'))
         t.throws(() => statSync(dir + '/c/f/i/m'))
       })
+
+      t.test('async filter', async t => {
+        const dir = t.testdir(fixture)
+        const saw = []
+        const filter = async p => {
+          saw.push(relative(process.cwd(), p).replace(/\\/g, '/'))
+          await new Promise(setImmediate)
+          return basename(p) !== f
+        }
+        await rimrafPosix(dir, { filter })
+        t.matchSnapshot(
+          saw.sort((a, b) => a.localeCompare(b, 'en')),
+          'paths seen'
+        )
+        statSync(dir)
+        statSync(dir + '/c')
+        statSync(dir + '/c/f')
+        statSync(dir + '/c/f/i')
+        if (f === 'j') {
+          statSync(dir + '/c/f/i/j')
+        } else {
+          t.throws(() => statSync(dir + '/c/f/i/j'))
+        }
+        t.throws(() => statSync(dir + '/a'))
+        t.throws(() => statSync(dir + '/b'))
+        t.throws(() => statSync(dir + '/c/d'))
+        t.throws(() => statSync(dir + '/c/e'))
+        t.throws(() => statSync(dir + '/c/f/g'))
+        t.throws(() => statSync(dir + '/c/f/h'))
+        t.throws(() => statSync(dir + '/c/f/i/k'))
+        t.throws(() => statSync(dir + '/c/f/i/l'))
+        t.throws(() => statSync(dir + '/c/f/i/m'))
+      })
       t.end()
     })
   }
diff --git a/test/rimraf-windows.js b/test/rimraf-windows.js
index 26b5605d..eca02e6e 100644
--- a/test/rimraf-windows.js
+++ b/test/rimraf-windows.js
@@ -602,6 +602,39 @@ t.test('filter function', t => {
         t.throws(() => statSync(dir + '/c/f/i/l'))
         t.throws(() => statSync(dir + '/c/f/i/m'))
       })
+
+      t.test('async filter', async t => {
+        const dir = t.testdir(fixture)
+        const saw = []
+        const filter = async p => {
+          saw.push(relative(process.cwd(), p).replace(/\\/g, '/'))
+          await new Promise(setImmediate)
+          return basename(p) !== f
+        }
+        await rimrafWindows(dir, { filter })
+        t.matchSnapshot(
+          saw.sort((a, b) => a.localeCompare(b, 'en')),
+          'paths seen'
+        )
+        statSync(dir)
+        statSync(dir + '/c')
+        statSync(dir + '/c/f')
+        statSync(dir + '/c/f/i')
+        if (f === 'j') {
+          statSync(dir + '/c/f/i/j')
+        } else {
+          t.throws(() => statSync(dir + '/c/f/i/j'))
+        }
+        t.throws(() => statSync(dir + '/a'))
+        t.throws(() => statSync(dir + '/b'))
+        t.throws(() => statSync(dir + '/c/d'))
+        t.throws(() => statSync(dir + '/c/e'))
+        t.throws(() => statSync(dir + '/c/f/g'))
+        t.throws(() => statSync(dir + '/c/f/h'))
+        t.throws(() => statSync(dir + '/c/f/i/k'))
+        t.throws(() => statSync(dir + '/c/f/i/l'))
+        t.throws(() => statSync(dir + '/c/f/i/m'))
+      })
       t.end()
     })
   }