diff --git a/test/helpers/create-https-test-server.ts b/test/helpers/create-https-test-server.ts
index 05b5c3565..494662367 100644
--- a/test/helpers/create-https-test-server.ts
+++ b/test/helpers/create-https-test-server.ts
@@ -5,6 +5,7 @@ import type {SecureContextOptions} from 'tls';
 import express from 'express';
 import pify from 'pify';
 import pem from 'pem';
+import type {CreateCSR, CreateCertificate} from '../types/pem.js';
 
 export type HttpsServerOptions = {
 	commonName?: string;
@@ -25,8 +26,8 @@ export type ExtendedHttpsTestServer = {
 } & express.Express;
 
 const createHttpsTestServer = async (options: HttpsServerOptions = {}): Promise<ExtendedHttpsTestServer> => {
-	const createCsr = pify(pem.createCSR);
-	const createCertificate = pify(pem.createCertificate);
+	const createCsr = pify(pem.createCSR as CreateCSR);
+	const createCertificate = pify(pem.createCertificate as CreateCertificate);
 
 	const caCsrResult = await createCsr({commonName: 'authority'});
 	const caResult = await createCertificate({
@@ -68,7 +69,7 @@ const createHttpsTestServer = async (options: HttpsServerOptions = {}): Promise<
 
 	await pify(server.https.listen.bind(server.https))();
 
-	server.caKey = caKey;
+	server.caKey = caKey as any;
 	server.caCert = caCert;
 	server.port = (server.https.address() as net.AddressInfo).port;
 	server.url = `https://localhost:${(server.port)}`;
diff --git a/test/https.ts b/test/https.ts
index e1b80ec75..0fa6f7f95 100644
--- a/test/https.ts
+++ b/test/https.ts
@@ -6,10 +6,11 @@ import pify from 'pify';
 import pem from 'pem';
 import got from '../source/index.js';
 import {withHttpsServer} from './helpers/with-server.js';
+import type {CreatePrivateKey, CreateCSR, CreateCertificate} from './types/pem.js';
 
-const createPrivateKey = pify(pem.createPrivateKey);
-const createCsr = pify(pem.createCSR);
-const createCertificate = pify(pem.createCertificate);
+const createPrivateKey = pify(pem.createPrivateKey as CreatePrivateKey);
+const createCsr = pify(pem.createCSR as CreateCSR);
+const createCertificate = pify(pem.createCertificate as CreateCertificate);
 const createPkcs12 = pify(pem.createPkcs12);
 
 test('https request without ca', withHttpsServer(), async (t, server, got) => {
diff --git a/test/types/pem.ts b/test/types/pem.ts
new file mode 100644
index 000000000..29c252ffe
--- /dev/null
+++ b/test/types/pem.ts
@@ -0,0 +1,19 @@
+import type {
+	CertificateCreationOptions,
+	CertificateCreationResult,
+	PrivateKeyCreationOptions,
+	CSRCreationOptions,
+	Callback
+} from 'pem';
+
+export interface CreateCertificate {
+	(options: CertificateCreationOptions, callback: Callback<CertificateCreationResult>): void
+}
+
+export interface CreateCSR {
+	(options: CSRCreationOptions, callback: Callback<{ csr: string, clientKey: string }>): void
+}
+
+export interface CreatePrivateKey {
+	(keyBitsize: number, options: PrivateKeyCreationOptions, callback: Callback<{ key: string }>): void
+}