diff --git a/index.d.ts b/index.d.ts
index 81ad662a9..da9dc5af7 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -10,7 +10,6 @@ declare namespace execa {
 		| 'inherit'
 		| Stream
 		| number
-		| null
 		| undefined;
 
 	interface CommonOptions<EncodingType> {
@@ -45,7 +44,7 @@ declare namespace execa {
 
 		@default 'pipe'
 		*/
-		readonly stdio?: 'pipe' | 'ignore' | 'inherit' | ReadonlyArray<StdioOption>;
+		readonly stdio?: 'pipe' | 'ignore' | 'inherit' | readonly StdioOption[];
 
 		/**
 		Prepare child to run independently of its parent process. Specific behavior [depends on the platform](https://nodejs.org/api/child_process.html#child_process_options_detached).
@@ -284,11 +283,7 @@ declare namespace execa {
 
 	interface ExecaChildPromise<StdoutErrorType> {
 		catch<ResultType = never>(
-			onRejected?:
-				| ((
-						reason: ExecaError<StdoutErrorType>
-				  ) => ResultType | PromiseLike<ResultType>)
-				| null
+			onRejected?: (reason: ExecaError<StdoutErrorType>) => ResultType | PromiseLike<ResultType>
 		): Promise<ExecaReturnValue<StdoutErrorType> | ResultType>;
 
 		/**
@@ -340,12 +335,12 @@ declare const execa: {
 	*/
 	(
 		file: string,
-		arguments?: ReadonlyArray<string>,
+		arguments?: readonly string[],
 		options?: execa.Options
 	): execa.ExecaChildProcess;
 	(
 		file: string,
-		arguments?: ReadonlyArray<string>,
+		arguments?: readonly string[],
 		options?: execa.Options<null>
 	): execa.ExecaChildProcess<Buffer>;
 	(file: string, options?: execa.Options): execa.ExecaChildProcess;
@@ -362,12 +357,12 @@ declare const execa: {
 	*/
 	stdout(
 		file: string,
-		arguments?: ReadonlyArray<string>,
+		arguments?: readonly string[],
 		options?: execa.Options
 	): Promise<string>;
 	stdout(
 		file: string,
-		arguments?: ReadonlyArray<string>,
+		arguments?: readonly string[],
 		options?: execa.Options<null>
 	): Promise<Buffer>;
 	stdout(file: string, options?: execa.Options): Promise<string>;
@@ -382,12 +377,12 @@ declare const execa: {
 	*/
 	stderr(
 		file: string,
-		arguments?: ReadonlyArray<string>,
+		arguments?: readonly string[],
 		options?: execa.Options
 	): Promise<string>;
 	stderr(
 		file: string,
-		arguments?: ReadonlyArray<string>,
+		arguments?: readonly string[],
 		options?: execa.Options<null>
 	): Promise<Buffer>;
 	stderr(file: string, options?: execa.Options): Promise<string>;
@@ -449,12 +444,12 @@ declare const execa: {
 	*/
 	sync(
 		file: string,
-		arguments?: ReadonlyArray<string>,
+		arguments?: readonly string[],
 		options?: execa.SyncOptions
 	): execa.ExecaSyncReturnValue;
 	sync(
 		file: string,
-		arguments?: ReadonlyArray<string>,
+		arguments?: readonly string[],
 		options?: execa.SyncOptions<null>
 	): execa.ExecaSyncReturnValue<Buffer>;
 	sync(file: string, options?: execa.SyncOptions): execa.ExecaSyncReturnValue;
diff --git a/index.js b/index.js
index 684989253..9899d2c48 100644
--- a/index.js
+++ b/index.js
@@ -69,7 +69,7 @@ function handleArgs(command, args, options) {
 }
 
 function handleInput(spawned, input) {
-	if (input === null || input === undefined) {
+	if (input === undefined) {
 		return;
 	}
 
diff --git a/index.test-d.ts b/index.test-d.ts
index 23c06591b..e89d9661d 100644
--- a/index.test-d.ts
+++ b/index.test-d.ts
@@ -61,7 +61,7 @@ execa('unicorns', {stdio: 'pipe'});
 execa('unicorns', {stdio: 'ignore'});
 execa('unicorns', {stdio: 'inherit'});
 execa('unicorns', {
-	stdio: ['pipe', 'ipc', 'ignore', 'inherit', process.stdin, 1, null, undefined]
+	stdio: ['pipe', 'ipc', 'ignore', 'inherit', process.stdin, 1, undefined]
 });
 execa('unicorns', {detached: true});
 execa('unicorns', {uid: 0});
@@ -84,7 +84,6 @@ execa('unicorns', {stdin: 'ignore'});
 execa('unicorns', {stdin: 'inherit'});
 execa('unicorns', {stdin: process.stdin});
 execa('unicorns', {stdin: 1});
-execa('unicorns', {stdin: null});
 execa('unicorns', {stdin: undefined});
 execa('unicorns', {stderr: 'pipe'});
 execa('unicorns', {stderr: 'ipc'});
@@ -92,7 +91,6 @@ execa('unicorns', {stderr: 'ignore'});
 execa('unicorns', {stderr: 'inherit'});
 execa('unicorns', {stderr: process.stderr});
 execa('unicorns', {stderr: 1});
-execa('unicorns', {stderr: null});
 execa('unicorns', {stderr: undefined});
 execa('unicorns', {stdout: 'pipe'});
 execa('unicorns', {stdout: 'ipc'});
@@ -100,7 +98,6 @@ execa('unicorns', {stdout: 'ignore'});
 execa('unicorns', {stdout: 'inherit'});
 execa('unicorns', {stdout: process.stdout});
 execa('unicorns', {stdout: 1});
-execa('unicorns', {stdout: null});
 execa('unicorns', {stdout: undefined});
 execa('unicorns', {windowsVerbatimArguments: true});
 
diff --git a/readme.md b/readme.md
index fd7931075..3dccd8581 100644
--- a/readme.md
+++ b/readme.md
@@ -162,7 +162,7 @@ Returns the same result object as [`child_process.spawnSync`](https://nodejs.org
 
 ### options
 
-Type: `Object`
+Type: `object`
 
 #### cwd
 
@@ -173,7 +173,7 @@ Current working directory of the child process.
 
 #### env
 
-Type: `Object`<br>
+Type: `object`<br>
 Default: `process.env`
 
 Environment key-value pairs. Extends automatically from `process.env`. Set `extendEnv` to `false` if you don't want this.
@@ -193,7 +193,7 @@ Explicitly set the value of `argv[0]` sent to the child process. This will be se
 
 #### stdio
 
-Type: `string[]` `string`<br>
+Type: `string | string[]`<br>
 Default: `pipe`
 
 Child's [stdio](https://nodejs.org/api/child_process.html#child_process_options_stdio) configuration.
@@ -218,7 +218,7 @@ Sets the group identity of the process.
 
 #### shell
 
-Type: `boolean` `string`<br>
+Type: `boolean | string`<br>
 Default: `false`
 
 If `true`, runs `command` inside of a shell. Uses `/bin/sh` on UNIX and `cmd.exe` on Windows. A different shell can be specified as a string. The shell should understand the `-c` switch on UNIX or `/d /s /c` on Windows.
@@ -247,7 +247,7 @@ Preferred path to find locally installed binaries in (use with `preferLocal`).
 
 #### input
 
-Type: `string` `Buffer` `stream.Readable`
+Type: `string | Buffer | stream.Readable`
 
 Write some input to the `stdin` of your binary.<br>
 Streams are not allowed when using the synchronous methods.
@@ -268,7 +268,7 @@ Keep track of the spawned process and `kill` it when the parent process exits.
 
 #### encoding
 
-Type: `string` `null`<br>
+Type: `string | null`<br>
 Default: `utf8`
 
 Specify the character encoding used to decode the `stdout` and `stderr` output. If set to `null`, then `stdout` and `stderr` will be a `Buffer` instead of a string.
@@ -296,28 +296,28 @@ Largest amount of data in bytes allowed on `stdout` or `stderr`.
 
 #### killSignal
 
-Type: `string` `number`<br>
+Type: `string | number`<br>
 Default: `SIGTERM`
 
 Signal value to be used when the spawned process will be killed.
 
 #### stdin
 
-Type: `string` `number` `Stream` `undefined` `null`<br>
+Type: `string | number | Stream | undefined`<br>
 Default: `pipe`
 
 Same options as [`stdio`](https://nodejs.org/dist/latest-v6.x/docs/api/child_process.html#child_process_options_stdio).
 
 #### stdout
 
-Type: `string` `number` `Stream` `undefined` `null`<br>
+Type: `string | number | Stream | undefined`<br>
 Default: `pipe`
 
 Same options as [`stdio`](https://nodejs.org/dist/latest-v6.x/docs/api/child_process.html#child_process_options_stdio).
 
 #### stderr
 
-Type: `string` `number` `Stream` `undefined` `null`<br>
+Type: `string | number | Stream | undefined`<br>
 Default: `pipe`
 
 Same options as [`stdio`](https://nodejs.org/dist/latest-v6.x/docs/api/child_process.html#child_process_options_stdio).
diff --git a/test.js b/test.js
index ffd98bdb1..07a3b0180 100644
--- a/test.js
+++ b/test.js
@@ -76,7 +76,7 @@ test('do not include `stderr` and `stdout` in errors when set to `inherit`', asy
 });
 
 test('do not include `stderr` and `stdout` in errors when `stdio` is set to `inherit`', async t => {
-	await t.throwsAsync(execa('fixtures/error-message.js', {stdio: [null, 'inherit', 'inherit']}), {message: NO_NEWLINES_REGEXP});
+	await t.throwsAsync(execa('fixtures/error-message.js', {stdio: [undefined, 'inherit', 'inherit']}), {message: NO_NEWLINES_REGEXP});
 });
 
 test('do not include `stdout` in errors when set to `inherit`', async t => {
@@ -213,7 +213,7 @@ test('input option can be a Buffer - sync', t => {
 test('opts.stdout:ignore - stdout will not collect data', async t => {
 	const {stdout} = await execa('stdin', {
 		input: 'hello',
-		stdio: [null, 'ignore', null]
+		stdio: [undefined, 'ignore', undefined]
 	});
 	t.is(stdout, undefined);
 });
diff --git a/test/stdio.js b/test/stdio.js
index e51fc7d8e..e02a32911 100644
--- a/test/stdio.js
+++ b/test/stdio.js
@@ -22,7 +22,6 @@ function macro(t, input, expected) {
 macro.title = (providedTitle, input) => providedTitle || util.inspect(input, {colors: true});
 
 test(macro, undefined, undefined);
-test(macro, null, undefined);
 
 test(macro, {stdio: 'inherit'}, 'inherit');
 test(macro, {stdio: 'pipe'}, 'pipe');