diff --git a/package.json b/package.json
index d8ce9ef0d..6b560cd90 100644
--- a/package.json
+++ b/package.json
@@ -65,7 +65,7 @@
 		"create-test-server": "^3.0.1",
 		"del-cli": "^3.0.0",
 		"delay": "^4.3.0",
-		"eslint-config-xo-typescript": "^0.19.0",
+		"eslint-config-xo-typescript": "^0.21.0",
 		"form-data": "^3.0.0",
 		"get-port": "^5.0.0",
 		"keyv": "^3.1.0",
@@ -115,9 +115,7 @@
 		],
 		"rules": {
 			"@typescript-eslint/explicit-function-return-type": "off",
-			"@typescript-eslint/promise-function-async": "off",
-			"@typescript-eslint/strict-boolean-expressions": "off",
-			"@typescript-eslint/no-unnecessary-condition": "off"
+			"@typescript-eslint/promise-function-async": "off"
 		},
 		"ignores": [
 			"documentation/examples/*"
diff --git a/source/as-promise.ts b/source/as-promise.ts
index e965cca8b..68be175c7 100644
--- a/source/as-promise.ts
+++ b/source/as-promise.ts
@@ -11,7 +11,7 @@ import requestAsEventEmitter from './request-as-event-emitter';
 
 type ResponseReturn = Response | Buffer | string | any;
 
-export const isProxiedSymbol = Symbol('proxied');
+export const isProxiedSymbol: unique symbol = Symbol('proxied');
 
 export default function asPromise(options: NormalizedOptions): CancelableRequest<Response> {
 	const proxy = new EventEmitter();
@@ -56,8 +56,8 @@ export default function asPromise(options: NormalizedOptions): CancelableRequest
 				return;
 			}
 
-			if (response.req && response.req.aborted) {
-				// Canceled while downloading - will throw a CancelError or TimeoutError
+			if (response.req?.aborted) {
+				// Canceled while downloading - will throw a `CancelError` or `TimeoutError` error
 				return;
 			}
 
@@ -123,14 +123,19 @@ export default function asPromise(options: NormalizedOptions): CancelableRequest
 		});
 
 		emitter.once('error', reject);
-		[
+
+		const events = [
 			'request',
 			'redirect',
 			'uploadProgress',
 			'downloadProgress'
-		].forEach(event => emitter.on(event, (...args: unknown[]) => {
-			proxy.emit(event, ...args);
-		}));
+		];
+
+		for (const event of events) {
+			emitter.on(event, (...args: unknown[]) => {
+				proxy.emit(event, ...args);
+			});
+		}
 	}) as CancelableRequest<ResponseReturn>;
 
 	promise[isProxiedSymbol] = true;
diff --git a/source/as-stream.ts b/source/as-stream.ts
index 38cd94780..b03f69f8c 100644
--- a/source/as-stream.ts
+++ b/source/as-stream.ts
@@ -82,8 +82,8 @@ export default function asStream(options: NormalizedOptions): ProxyStream {
 			for (const [key, value] of Object.entries(response.headers)) {
 				// Got gives *decompressed* data. Overriding `content-encoding` header would result in an error.
 				// It's not possible to decompress already decompressed data, is it?
-				const allowed = options.decompress ? key !== 'content-encoding' : true;
-				if (allowed) {
+				const isAllowed = options.decompress ? key !== 'content-encoding' : true;
+				if (isAllowed) {
 					destination.setHeader(key, value);
 				}
 			}
diff --git a/source/calculate-retry-delay.ts b/source/calculate-retry-delay.ts
index 9fc2ecdd4..7f4bf3874 100644
--- a/source/calculate-retry-delay.ts
+++ b/source/calculate-retry-delay.ts
@@ -16,6 +16,7 @@ const calculateRetryDelay: RetryFunction = ({attemptCount, retryOptions, error})
 		return 0;
 	}
 
+	// TODO: This type coercion is not entirely correct as it makes `response` a guaranteed property, when it's in fact not.
 	const {response} = error as HTTPError | ParseError | MaxRedirectsError;
 	if (response && Reflect.has(response.headers, 'retry-after') && retryAfterStatusCodes.has(response.statusCode)) {
 		let after = Number(response.headers['retry-after']);
@@ -32,7 +33,7 @@ const calculateRetryDelay: RetryFunction = ({attemptCount, retryOptions, error})
 		return after;
 	}
 
-	if (response && response.statusCode === 413) {
+	if (response?.statusCode === 413) {
 		return 0;
 	}
 
diff --git a/source/create.ts b/source/create.ts
index 55687f6e3..8ca80ebf0 100644
--- a/source/create.ts
+++ b/source/create.ts
@@ -18,10 +18,16 @@ import asStream, {ProxyStream} from './as-stream';
 import {preNormalizeArguments, normalizeArguments} from './normalize-arguments';
 import {Hooks} from './known-hook-events';
 
-export type HTTPAlias = 'get' | 'post' | 'put' | 'patch' | 'head' | 'delete';
-
-export type ReturnResponse = (url: URLArgument | Options & { stream?: false; url: URLArgument }, options?: Options & { stream?: false }) => CancelableRequest<Response>;
-export type ReturnStream = (url: URLArgument | Options & { stream: true; url: URLArgument }, options?: Options & { stream: true }) => ProxyStream;
+export type HTTPAlias =
+	| 'get'
+	| 'post'
+	| 'put'
+	| 'patch'
+	| 'head'
+	| 'delete';
+
+export type ReturnResponse = (url: URLArgument | Options & {stream?: false; url: URLArgument}, options?: Options & {stream?: false}) => CancelableRequest<Response>;
+export type ReturnStream = (url: URLArgument | Options & {stream: true; url: URLArgument}, options?: Options & {stream: true}) => ProxyStream;
 export type GotReturn = ProxyStream | CancelableRequest<Response>;
 
 const getPromiseOrStream = (options: NormalizedOptions): GotReturn => options.stream ? asStream(options) : asPromise(options);
@@ -40,13 +46,13 @@ export interface Got extends Record<HTTPAlias, ReturnResponse> {
 	TimeoutError: typeof errors.TimeoutError;
 	CancelError: typeof errors.CancelError;
 
-	(url: URLArgument | Options & { stream?: false; url: URLArgument }, options?: Options & { stream?: false }): CancelableRequest<Response>;
-	(url: URLArgument | Options & { stream: true; url: URLArgument }, options?: Options & { stream: true }): ProxyStream;
+	(url: URLArgument | Options & {stream?: false; url: URLArgument}, options?: Options & {stream?: false}): CancelableRequest<Response>;
+	(url: URLArgument | Options & {stream: true; url: URLArgument}, options?: Options & {stream: true}): ProxyStream;
 	(url: URLOrOptions, options?: Options): CancelableRequest<Response> | ProxyStream;
 	create(defaults: Defaults): Got;
 	extend(...instancesOrOptions: Array<Got | ExtendedOptions>): Got;
 	mergeInstances(parent: Got, ...instances: Got[]): Got;
-	mergeOptions<T extends Options>(...sources: T[]): T & { hooks: Partial<Hooks> };
+	mergeOptions<T extends Options>(...sources: T[]): T & {hooks: Partial<Hooks>};
 }
 
 export interface GotStream extends Record<HTTPAlias, ReturnStream> {
@@ -76,7 +82,7 @@ const create = (nonNormalizedDefaults: Defaults): Got => {
 
 	// @ts-ignore Because the for loop handles it for us, as well as the other Object.defines
 	const got: Got = (url: URLOrOptions, options?: Options): GotReturn => {
-		const isStream = options && options.stream;
+		const isStream = options?.stream ?? false;
 
 		let iteration = 0;
 		const iterateHandlers = (newOptions: NormalizedOptions): GotReturn => {
@@ -97,9 +103,7 @@ const create = (nonNormalizedDefaults: Defaults): Got => {
 			if (!isStream && !Reflect.has(result, isProxiedSymbol)) {
 				for (const key of Object.keys(nextPromise)) {
 					Object.defineProperty(result, key, {
-						get: () => {
-							return nextPromise[key];
-						},
+						get: () => nextPromise[key],
 						set: (value: unknown) => {
 							nextPromise[key] = value;
 						}
diff --git a/source/errors.ts b/source/errors.ts
index 483ecdae1..68248c1b0 100644
--- a/source/errors.ts
+++ b/source/errors.ts
@@ -6,8 +6,7 @@ import {TimeoutError as TimedOutError} from './utils/timed-out';
 
 export class GotError extends Error {
 	code?: string;
-
-	readonly options!: NormalizedOptions;
+	readonly options: NormalizedOptions;
 
 	constructor(message: string, error: (Error & {code?: string}) | {code?: string}, options: NormalizedOptions) {
 		super(message);
@@ -46,7 +45,7 @@ export class ReadError extends GotError {
 }
 
 export class ParseError extends GotError {
-	readonly response!: Response;
+	readonly response: Response;
 
 	constructor(error: Error, response: Response, options: NormalizedOptions) {
 		super(`${error.message} in "${format(options as unknown as URL)}"`, error, options);
@@ -59,7 +58,7 @@ export class ParseError extends GotError {
 }
 
 export class HTTPError extends GotError {
-	readonly response!: Response;
+	readonly response: Response;
 
 	constructor(response: Response, options: NormalizedOptions) {
 		const {statusCode, statusMessage} = response;
@@ -74,7 +73,7 @@ export class HTTPError extends GotError {
 }
 
 export class MaxRedirectsError extends GotError {
-	readonly response!: Response;
+	readonly response: Response;
 
 	constructor(response: Response, maxRedirects: number, options: NormalizedOptions) {
 		super(`Redirected ${maxRedirects} times. Aborting.`, {}, options);
@@ -95,7 +94,6 @@ export class UnsupportedProtocolError extends GotError {
 
 export class TimeoutError extends GotError {
 	timings: Timings;
-
 	event: string;
 
 	constructor(error: TimedOutError, timings: Timings, options: NormalizedOptions) {
diff --git a/source/get-response.ts b/source/get-response.ts
index 3c0ef515c..57707963d 100644
--- a/source/get-response.ts
+++ b/source/get-response.ts
@@ -19,7 +19,7 @@ export default (response: IncomingMessage, options: NormalizedOptions, emitter:
 		options.method !== 'HEAD' ? decompressResponse(progressStream as unknown as IncomingMessage) : progressStream
 	) as Response;
 
-	if (!options.decompress && ['gzip', 'deflate', 'br'].includes(response.headers['content-encoding'] || '')) {
+	if (!options.decompress && ['gzip', 'deflate', 'br'].includes(response.headers['content-encoding'] ?? '')) {
 		options.encoding = null;
 	}
 
diff --git a/source/merge.ts b/source/merge.ts
index 048bf65f5..df6fb4d7f 100644
--- a/source/merge.ts
+++ b/source/merge.ts
@@ -67,34 +67,36 @@ export function mergeOptions(...sources: Array<Partial<Options>>): Partial<Optio
 
 	for (const source of sources) {
 		// We need to check `source` to allow calling `.extend()` with no arguments.
-		if (source) {
-			if (Reflect.has(source, 'hooks')) {
-				for (const hook of knownHookEvents) {
-					hooks[hook] = hooks[hook].concat(source.hooks[hook] || []);
-				}
-			}
+		if (!source) {
+			continue;
+		}
 
-			if (Reflect.has(source, 'context')) {
-				Object.defineProperty(mergedOptions, 'context', {
-					writable: true,
-					configurable: true,
-					enumerable: false,
-					// @ts-ignore
-					value: source.context
-				});
+		if (Reflect.has(source, 'hooks')) {
+			for (const hook of knownHookEvents) {
+				hooks[hook] = hooks[hook].concat(source.hooks[hook] ?? []);
 			}
+		}
 
-			if (Reflect.has(source, 'body')) {
-				mergedOptions.body = source.body;
-			}
+		if (Reflect.has(source, 'context')) {
+			Object.defineProperty(mergedOptions, 'context', {
+				writable: true,
+				configurable: true,
+				enumerable: false,
+				// @ts-ignore
+				value: source.context
+			});
+		}
 
-			if (Reflect.has(source, 'json')) {
-				mergedOptions.json = source.json;
-			}
+		if (Reflect.has(source, 'body')) {
+			mergedOptions.body = source.body;
+		}
 
-			if (Reflect.has(source, 'form')) {
-				mergedOptions.form = source.form;
-			}
+		if (Reflect.has(source, 'json')) {
+			mergedOptions.json = source.json;
+		}
+
+		if (Reflect.has(source, 'form')) {
+			mergedOptions.form = source.form;
 		}
 	}
 
diff --git a/source/normalize-arguments.ts b/source/normalize-arguments.ts
index 6bcdefde7..8515f3eef 100644
--- a/source/normalize-arguments.ts
+++ b/source/normalize-arguments.ts
@@ -119,7 +119,7 @@ export const normalizeArguments = (url: URLOrOptions, options: Options, defaults
 	let urlArgument: URLArgument;
 	if (is.plainObject(url)) {
 		options = {...url as Options, ...options};
-		urlArgument = options.url || {};
+		urlArgument = options.url ?? {};
 		delete options.url;
 	} else {
 		urlArgument = url;
@@ -200,6 +200,7 @@ export const normalizeArguments = (url: URLOrOptions, options: Options, defaults
 	if (is.nonEmptyString(searchParams) || is.nonEmptyObject(searchParams) || (searchParams && searchParams instanceof URLSearchParams)) {
 		if (!is.string(searchParams)) {
 			if (!(searchParams instanceof URLSearchParams)) {
+				// @ts-ignore
 				validateSearchParams(searchParams);
 			}
 
@@ -212,7 +213,7 @@ export const normalizeArguments = (url: URLOrOptions, options: Options, defaults
 	if (options.hostname === 'unix') {
 		const matches = /(?<socketPath>.+?):(?<path>.+)/.exec(options.path);
 
-		if (matches && matches.groups) {
+		if (matches?.groups) {
 			const {socketPath, path} = matches.groups;
 			options = {
 				...options,
diff --git a/source/progress.ts b/source/progress.ts
index 08b6f70ca..8c98db75e 100644
--- a/source/progress.ts
+++ b/source/progress.ts
@@ -4,19 +4,19 @@ import {Socket} from 'net';
 import EventEmitter = require('events');
 
 export function downloadProgress(_response: IncomingMessage, emitter: EventEmitter, downloadBodySize?: number): TransformStream {
-	let downloaded = 0;
+	let downloadedBytes = 0;
 
 	return new TransformStream({
 		transform(chunk, _encoding, callback) {
-			downloaded += chunk.length;
+			downloadedBytes += chunk.length;
 
-			const percent = downloadBodySize ? downloaded / downloadBodySize : 0;
+			const percent = downloadBodySize ? downloadedBytes / downloadBodySize : 0;
 
 			// Let `flush()` be responsible for emitting the last event
 			if (percent < 1) {
 				emitter.emit('downloadProgress', {
 					percent,
-					transferred: downloaded,
+					transferred: downloadedBytes,
 					total: downloadBodySize
 				});
 			}
@@ -27,7 +27,7 @@ export function downloadProgress(_response: IncomingMessage, emitter: EventEmitt
 		flush(callback) {
 			emitter.emit('downloadProgress', {
 				percent: 1,
-				transferred: downloaded,
+				transferred: downloadedBytes,
 				total: downloadBodySize
 			});
 
@@ -38,7 +38,7 @@ export function downloadProgress(_response: IncomingMessage, emitter: EventEmitt
 
 export function uploadProgress(request: ClientRequest, emitter: EventEmitter, uploadBodySize?: number): void {
 	const uploadEventFrequency = 150;
-	let uploaded = 0;
+	let uploadedBytes = 0;
 	let progressInterval: NodeJS.Timeout;
 
 	emitter.emit('uploadProgress', {
@@ -56,7 +56,7 @@ export function uploadProgress(request: ClientRequest, emitter: EventEmitter, up
 
 		emitter.emit('uploadProgress', {
 			percent: 1,
-			transferred: uploaded,
+			transferred: uploadedBytes,
 			total: uploadBodySize
 		});
 	});
@@ -64,21 +64,21 @@ export function uploadProgress(request: ClientRequest, emitter: EventEmitter, up
 	request.once('socket', (socket: Socket) => {
 		const onSocketConnect = (): void => {
 			progressInterval = setInterval(() => {
-				const lastUploaded = uploaded;
+				const lastUploadedBytes = uploadedBytes;
 				/* istanbul ignore next: see #490 (occurs randomly!) */
 				const headersSize = (request as any)._header ? Buffer.byteLength((request as any)._header) : 0;
-				uploaded = socket.bytesWritten - headersSize;
+				uploadedBytes = socket.bytesWritten - headersSize;
 
 				// Don't emit events with unchanged progress and
 				// prevent last event from being emitted, because
 				// it's emitted when `response` is emitted
-				if (uploaded === lastUploaded || uploaded === uploadBodySize) {
+				if (uploadedBytes === lastUploadedBytes || uploadedBytes === uploadBodySize) {
 					return;
 				}
 
 				emitter.emit('uploadProgress', {
-					percent: uploadBodySize ? uploaded / uploadBodySize : 0,
-					transferred: uploaded,
+					percent: uploadBodySize ? uploadedBytes / uploadBodySize : 0,
+					transferred: uploadedBytes,
 					total: uploadBodySize
 				});
 			}, uploadEventFrequency);
diff --git a/source/request-as-event-emitter.ts b/source/request-as-event-emitter.ts
index 2c07ef715..aa572e5cc 100644
--- a/source/request-as-event-emitter.ts
+++ b/source/request-as-event-emitter.ts
@@ -30,17 +30,17 @@ export interface RequestAsEventEmitter extends EventEmitter {
 
 export default (options: NormalizedOptions, input?: TransformStream) => {
 	const emitter = new EventEmitter() as RequestAsEventEmitter;
-	const redirects = [] as string[];
+	const redirects: string[] = [];
 	let currentRequest: http.ClientRequest;
 	let requestUrl: string;
-	let redirectString: string;
+	let redirectString: string | undefined;
 	let uploadBodySize: number | undefined;
 	let retryCount = 0;
 	let shouldAbort = false;
 
-	const setCookie = options.cookieJar ? promisify(options.cookieJar.setCookie.bind(options.cookieJar)) : null;
-	const getCookieString = options.cookieJar ? promisify(options.cookieJar.getCookieString.bind(options.cookieJar)) : null;
-	const agents = is.object(options.agent) ? options.agent : null;
+	const setCookie = options.cookieJar && promisify(options.cookieJar.setCookie.bind(options.cookieJar));
+	const getCookieString = options.cookieJar && promisify(options.cookieJar.getCookieString.bind(options.cookieJar));
+	const agents = is.object(options.agent) && options.agent;
 
 	const emitError = async (error: Error): Promise<void> => {
 		try {
@@ -56,12 +56,13 @@ export default (options: NormalizedOptions, input?: TransformStream) => {
 	};
 
 	const get = async (options: NormalizedOptions): Promise<void> => {
-		const currentUrl = redirectString || requestUrl;
+		const currentUrl = redirectString ?? requestUrl;
 
 		if (options.protocol !== 'http:' && options.protocol !== 'https:') {
 			throw new UnsupportedProtocolError(options);
 		}
 
+		// Validate the URL
 		decodeURI(currentUrl);
 
 		let requestFn: RequestFunction;
@@ -73,15 +74,15 @@ export default (options: NormalizedOptions, input?: TransformStream) => {
 
 		if (agents) {
 			const protocolName = options.protocol === 'https:' ? 'https' : 'http';
-			options.agent = (agents as AgentByProtocol)[protocolName] || options.agent;
+			options.agent = (agents as AgentByProtocol)[protocolName] ?? options.agent;
 		}
 
 		/* istanbul ignore next: electron.net is broken */
 		// No point in typing process.versions correctly, as
-		// process.version.electron is used only once, right here.
+		// `process.version.electron` is used only once, right here.
 		if (options.useElectronNet && (process.versions as any).electron) {
-			const electron = dynamicRequire(module, 'electron'); // Trick webpack
-			requestFn = (electron as any).net.request || (electron as any).remote.net.request;
+			const electron = dynamicRequire(module, 'electron') as any; // Trick Webpack
+			requestFn = electron.net.request ?? electron.remote.net.request;
 		}
 
 		if (options.cookieJar) {
@@ -113,6 +114,7 @@ export default (options: NormalizedOptions, input?: TransformStream) => {
 
 				const {statusCode} = response;
 				const typedResponse = response as Response;
+				// This is intentionally using `||` over `??` so it can also catch empty status message.
 				typedResponse.statusMessage = typedResponse.statusMessage || http.STATUS_CODES[statusCode];
 				typedResponse.url = currentUrl;
 				typedResponse.requestUrl = requestUrl;
@@ -120,11 +122,11 @@ export default (options: NormalizedOptions, input?: TransformStream) => {
 				typedResponse.timings = timings;
 				typedResponse.redirectUrls = redirects;
 				typedResponse.request = {options};
-				typedResponse.isFromCache = typedResponse.fromCache || false;
+				typedResponse.isFromCache = typedResponse.fromCache ?? false;
 				delete typedResponse.fromCache;
 
 				if (!typedResponse.isFromCache) {
-					// @ts-ignore Node typings haven't been updated yet
+					// @ts-ignore Node.js typings haven't been updated yet
 					typedResponse.ip = response.socket.remoteAddress;
 				}
 
@@ -225,7 +227,7 @@ export default (options: NormalizedOptions, input?: TransformStream) => {
 				}
 
 				// No need to attach an error handler here,
-				// as `stream.pipeline(...)` doesn't remove this handler
+				// as `stream.pipeline(…)` doesn't remove this handler
 				// to allow stream reuse.
 
 				request.emit('upload-complete');
@@ -248,8 +250,9 @@ export default (options: NormalizedOptions, input?: TransformStream) => {
 					const {body} = options;
 					delete options.body;
 
-					// `stream.pipeline(...)` does it for us.
+					// `stream.pipeline(…)` handles `error` for us.
 					request.removeListener('error', onError);
+
 					stream.pipeline(
 						body,
 						request,
@@ -292,7 +295,7 @@ export default (options: NormalizedOptions, input?: TransformStream) => {
 
 			cacheRequest.once('request', handleRequest);
 		} else {
-			// Catches errors thrown by calling requestFn(...)
+			// Catches errors thrown by calling `requestFn(…)`
 			try {
 				// @ts-ignore TS complains that URLSearchParams is not the same as URLSearchParams
 				handleRequest(requestFn(options as unknown as URL, handleResponse));
@@ -376,7 +379,7 @@ export default (options: NormalizedOptions, input?: TransformStream) => {
 
 				if (is.object(body) && isFormData(body)) {
 					// Special case for https://github.com/form-data/form-data
-					headers['content-type'] = headers['content-type'] || `multipart/form-data; boundary=${body.getBoundary()}`;
+					headers['content-type'] = headers['content-type'] ?? `multipart/form-data; boundary=${body.getBoundary()}`;
 				} else if (!is.nodeStream(body) && !is.string(body) && !is.buffer(body)) {
 					throw new TypeError('The `body` option must be a stream.Readable, string or Buffer');
 				}
@@ -385,10 +388,10 @@ export default (options: NormalizedOptions, input?: TransformStream) => {
 					throw new TypeError('The `form` option must be an Object');
 				}
 
-				headers['content-type'] = headers['content-type'] || 'application/x-www-form-urlencoded';
+				headers['content-type'] = headers['content-type'] ?? 'application/x-www-form-urlencoded';
 				options.body = (new URLSearchParams(options.form as Record<string, string>)).toString();
 			} else if (isJSON) {
-				headers['content-type'] = headers['content-type'] || 'application/json';
+				headers['content-type'] = headers['content-type'] ?? 'application/json';
 				options.body = JSON.stringify(options.json);
 			}
 
@@ -410,7 +413,7 @@ export default (options: NormalizedOptions, input?: TransformStream) => {
 				options.headers.accept = 'application/json';
 			}
 
-			requestUrl = options.href || (new URL(options.path, format(options as UrlObject))).toString();
+			requestUrl = options.href ?? (new URL(options.path, format(options as UrlObject))).toString();
 
 			await get(options);
 		} catch (error) {
diff --git a/source/utils/dynamic-require.ts b/source/utils/dynamic-require.ts
index 11887dfc8..515f71995 100644
--- a/source/utils/dynamic-require.ts
+++ b/source/utils/dynamic-require.ts
@@ -1,5 +1,3 @@
 /* istanbul ignore file: used for webpack */
 
-export default (moduleObject: NodeModule, moduleId: string): unknown => {
-	return moduleObject.require(moduleId);
-};
+export default (moduleObject: NodeModule, moduleId: string): unknown => moduleObject.require(moduleId);
diff --git a/source/utils/timed-out.ts b/source/utils/timed-out.ts
index 5d05d78d2..27701e676 100644
--- a/source/utils/timed-out.ts
+++ b/source/utils/timed-out.ts
@@ -3,7 +3,7 @@ import {ClientRequest, IncomingMessage} from 'http';
 import {Delays} from './types';
 import unhandler from './unhandle';
 
-const reentry = Symbol('reentry');
+const reentry: unique symbol = Symbol('reentry');
 const noop = (): void => {};
 
 interface TimedOutOptions {
@@ -43,10 +43,7 @@ export default (request: ClientRequest, delays: Delays, options: TimedOutOptions
 			immediate.unref();
 		}, delay);
 
-		/* istanbul ignore next: in order to support electron renderer */
-		if (timeout.unref) {
-			timeout.unref();
-		}
+		timeout.unref?.();
 
 		const cancel = (): void => {
 			clearTimeout(timeout);
@@ -103,12 +100,14 @@ export default (request: ClientRequest, delays: Delays, options: TimedOutOptions
 	}
 
 	once(request, 'socket', (socket: net.Socket): void => {
-		// TODO: There seems to not be a 'socketPath' on the request, but there IS a socket.remoteAddress
+		// TODO: There seems to not be a `socketPath` on the request, but there *is* a `socket.remoteAddress`.
 		const {socketPath} = request as any;
 
 		/* istanbul ignore next: hard to test */
 		if (socket.connecting) {
-			if (typeof delays.lookup !== 'undefined' && !socketPath && !net.isIP(hostname || host || '') && typeof (socket.address() as net.AddressInfo).address === 'undefined') {
+			const hasPath = Boolean(socketPath ?? net.isIP(hostname ?? host ?? '') !== 0);
+
+			if (typeof delays.lookup !== 'undefined' && !hasPath && typeof (socket.address() as net.AddressInfo).address === 'undefined') {
 				const cancelTimeout = addTimeout(delays.lookup, timeoutHandler, 'lookup');
 				once(socket, 'lookup', cancelTimeout);
 			}
@@ -116,7 +115,7 @@ export default (request: ClientRequest, delays: Delays, options: TimedOutOptions
 			if (typeof delays.connect !== 'undefined') {
 				const timeConnect = (): (() => void) => addTimeout(delays.connect, timeoutHandler, 'connect');
 
-				if (socketPath || net.isIP(hostname || host || '')) {
+				if (hasPath) {
 					once(socket, 'connect', timeConnect());
 				} else {
 					once(socket, 'lookup', (error: Error): void => {
diff --git a/source/utils/validate-search-params.ts b/source/utils/validate-search-params.ts
index f02f9c3bd..561d703c6 100644
--- a/source/utils/validate-search-params.ts
+++ b/source/utils/validate-search-params.ts
@@ -1,6 +1,6 @@
 import is from '@sindresorhus/is';
 
-export default (searchParams: Record<string, unknown>): void => {
+export default (searchParams: Record<string, unknown>): asserts searchParams is Record<string, string | number | boolean | null> => {
 	for (const value of Object.values(searchParams)) {
 		if (!is.string(value) && !is.number(value) && !is.boolean(value) && !is.null_(value)) {
 			throw new TypeError(`The \`searchParams\` value '${value}' must be a string, number, boolean or null`);
diff --git a/test/cookies.ts b/test/cookies.ts
index 71a305f23..4773df871 100644
--- a/test/cookies.ts
+++ b/test/cookies.ts
@@ -50,7 +50,7 @@ test('cookies doesn\'t break on redirects', withServer, async (t, server, got) =
 	});
 
 	server.get('/', (request, response) => {
-		response.end(request.headers.cookie || '');
+		response.end(request.headers.cookie ?? '');
 	});
 
 	const cookieJar = new toughCookie.CookieJar();
@@ -108,7 +108,7 @@ test('overrides options.headers.cookie', withServer, async (t, server, got) => {
 	});
 
 	server.get('/', (request, response) => {
-		response.end(request.headers.cookie || '');
+		response.end(request.headers.cookie ?? '');
 	});
 
 	const cookieJar = new toughCookie.CookieJar();
diff --git a/test/stream.ts b/test/stream.ts
index 88add5b28..848d92f12 100644
--- a/test/stream.ts
+++ b/test/stream.ts
@@ -113,7 +113,7 @@ test('has error event', withServer, async (t, server, got) => {
 });
 
 test('has error event #2', withServer, async (t, _server, got) => {
-	const stream = got.stream('http://doesntexist', {prefixUrl: null});
+	const stream = got.stream('http://doesntexist', {prefixUrl: ''});
 	await t.throwsAsync(pEvent(stream, 'response'), {code: 'ENOTFOUND'});
 });