diff --git a/lib/index.ts b/lib/index.ts
index 4c3033a..0baabe3 100644
--- a/lib/index.ts
+++ b/lib/index.ts
@@ -1,4 +1,4 @@
-import { FastifyPluginAsync, FastifyRequest } from 'fastify'
+import { type FastifyPluginAsync, type FastifyRequest } from 'fastify'
 import FastifyPlugin from 'fastify-plugin'
 import type { Fields, File, Files, Options } from 'formidable'
 // Since, formidable is CommonJS module
@@ -7,7 +7,7 @@ import type { Fields, File, Files, Options } from 'formidable'
 import FormidableNamespace from 'formidable'
 import type Formidable from 'formidable/Formidable'
 import * as fs from 'fs'
-import { IncomingMessage } from 'http'
+import { type IncomingMessage } from 'http'
 export const kIsMultipart = Symbol.for('[FastifyMultipart.isMultipart]')
 export const kIsMultipartParsed = Symbol.for('[FastifyMultipart.isMultipartParsed]')
 export const kFileSavedPaths = Symbol.for('[FastifyMultipart.fileSavedPaths]')
@@ -30,7 +30,7 @@ export interface FastifyFormidableOptions {
   formidable?: Formidable | Options
 }
 
-function promisify (func: Function): (request: IncomingMessage) => Promise<{ fields: Fields, files: Files }> {
+function promisify (func: (request: IncomingMessage, callback: (err: any, fields: Fields, files: Files) => void) => void): (request: IncomingMessage) => Promise<{ fields: Fields, files: Files }> {
   return async function (request: IncomingMessage): Promise<{ fields: Fields, files: Files }> {
     return await new Promise(function (resolve, reject) {
       func(request, function (err: any, fields: Fields, files: Files) {
diff --git a/test/addContentTypeParser.test.ts b/test/addContentTypeParser.test.ts
index 5e199ae..fa92dac 100644
--- a/test/addContentTypeParser.test.ts
+++ b/test/addContentTypeParser.test.ts
@@ -1,5 +1,5 @@
 import * as fs from 'fs'
-import { AddressInfo } from 'net'
+import { type AddressInfo } from 'net'
 import * as path from 'path'
 import t from 'tap'
 import { createFastify } from './createFastify'
diff --git a/test/addHooks.test.ts b/test/addHooks.test.ts
index b381a10..b00761c 100644
--- a/test/addHooks.test.ts
+++ b/test/addHooks.test.ts
@@ -1,5 +1,5 @@
 import * as fs from 'fs'
-import { AddressInfo } from 'net'
+import { type AddressInfo } from 'net'
 import * as path from 'path'
 import t from 'tap'
 import { createFastify } from './createFastify'
diff --git a/test/createFastify.ts b/test/createFastify.ts
index 77c4838..a6cc825 100644
--- a/test/createFastify.ts
+++ b/test/createFastify.ts
@@ -1,7 +1,7 @@
 import fastifySwagger from '@fastify/swagger'
-import Fastify, { FastifyInstance } from 'fastify'
-import { Options } from 'formidable'
-import FastifyFormidable, { ajvBinaryFormat, FastifyFormidableOptions } from '../lib'
+import Fastify, { type FastifyInstance } from 'fastify'
+import { type Options } from 'formidable'
+import FastifyFormidable, { ajvBinaryFormat, type FastifyFormidableOptions } from '../lib'
 
 // reduce keep alive to prevent `undici` keep the socket open
 export const fastifyOptions = { keepAliveTimeout: 100 }
@@ -11,7 +11,7 @@ export async function createFastify (t: Tap.Test, options: FastifyFormidableOpti
 
   await fastify.register(FastifyFormidable, options)
 
-  fastify.post<{ Body: { foo: String, file: string } }>('/', async function (request, reply) {
+  fastify.post<{ Body: { foo: string, file: string } }>('/', async function (request, reply) {
     if (inline === true) await request.parseMultipart()
     if (typeof inline === 'object') await request.parseMultipart(inline)
     return await reply.code(200).send({
@@ -38,7 +38,7 @@ export async function createIntegrationFastify (t: Tap.Test, options: FastifyFor
   await fastify.register(FastifyFormidable, options)
   await fastify.register(fastifySwagger)
 
-  fastify.post<{ Body: { foo: String, file: string } }>('/', {
+  fastify.post<{ Body: { foo: string, file: string } }>('/', {
     schema
   }, async function (request, reply) {
     if (inline) await request.parseMultipart()
diff --git a/test/error.test.ts b/test/error.test.ts
index a47d0b0..f69f6e7 100644
--- a/test/error.test.ts
+++ b/test/error.test.ts
@@ -1,7 +1,7 @@
 import Fastify from 'fastify'
 import { IncomingForm } from 'formidable'
 import * as fs from 'fs'
-import { AddressInfo } from 'net'
+import { type AddressInfo } from 'net'
 import * as path from 'path'
 import t from 'tap'
 import FastifyFormidable from '../lib'
@@ -36,8 +36,7 @@ t.test('error', function (t) {
     t.teardown(fastify.close)
 
     const formidable = new IncomingForm()
-    // @ts-expect-error
-    formidable.parse = function (_, callback: Function) {
+    formidable.parse = function (_, callback: (err: any) => void) {
       callback(new Error('parse error'))
     }
 
@@ -45,7 +44,7 @@ t.test('error', function (t) {
       formidable
     })
 
-    fastify.post<{ Body: { foo: String, file: string } }>('/', async function (request, reply) {
+    fastify.post<{ Body: { foo: string, file: string } }>('/', async function (request, reply) {
       const body = await request.parseMultipart()
       return await reply.code(200).send({
         body,
diff --git a/test/integration.test.ts b/test/integration.test.ts
index c44b410..116c21b 100644
--- a/test/integration.test.ts
+++ b/test/integration.test.ts
@@ -1,5 +1,5 @@
 import * as fs from 'fs'
-import { AddressInfo } from 'net'
+import { type AddressInfo } from 'net'
 import * as path from 'path'
 import t from 'tap'
 import { createIntegrationFastify } from './createFastify'
diff --git a/test/parseMultipart.test.ts b/test/parseMultipart.test.ts
index 63f64f4..f377b42 100644
--- a/test/parseMultipart.test.ts
+++ b/test/parseMultipart.test.ts
@@ -1,5 +1,5 @@
 import * as fs from 'fs'
-import { AddressInfo } from 'net'
+import { type AddressInfo } from 'net'
 import * as path from 'path'
 import t from 'tap'
 import { createFastify } from './createFastify'
diff --git a/test/removeFilesFromBody.test.ts b/test/removeFilesFromBody.test.ts
index 3678314..e801151 100644
--- a/test/removeFilesFromBody.test.ts
+++ b/test/removeFilesFromBody.test.ts
@@ -1,6 +1,6 @@
 import Fastify from 'fastify'
 import * as fs from 'fs'
-import { AddressInfo } from 'net'
+import { type AddressInfo } from 'net'
 import * as path from 'path'
 import t from 'tap'
 import FastifyFormidable from '../lib'
@@ -26,7 +26,7 @@ t.test('removeFilesFromBody', function (t) {
       removeFilesFromBody: true
     })
 
-    fastify.post<{ Body: { foo: String, file: string } }>('/', async function (request, reply) {
+    fastify.post<{ Body: { foo: string, file: string } }>('/', async function (request, reply) {
       return await reply.code(200).send({
         body: request.body,
         files: request.files
@@ -63,7 +63,7 @@ t.test('removeFilesFromBody', function (t) {
       removeFilesFromBody: true
     })
 
-    fastify.post<{ Body: { foo: String, file: string } }>('/', async function (request, reply) {
+    fastify.post<{ Body: { foo: string, file: string } }>('/', async function (request, reply) {
       return await reply.code(200).send({
         body: request.body,
         files: request.files
@@ -99,7 +99,7 @@ t.test('removeFilesFromBody', function (t) {
       removeFilesFromBody: true
     })
 
-    fastify.post<{ Body: { foo: String, file: string } }>('/', async function (request, reply) {
+    fastify.post<{ Body: { foo: string, file: string } }>('/', async function (request, reply) {
       const body = await request.parseMultipart()
       return await reply.code(200).send({
         body,
@@ -137,7 +137,7 @@ t.test('removeFilesFromBody', function (t) {
       removeFilesFromBody: true
     })
 
-    fastify.post<{ Body: { foo: String, file: string } }>('/', async function (request, reply) {
+    fastify.post<{ Body: { foo: string, file: string } }>('/', async function (request, reply) {
       return await reply.code(200).send({
         body: request.body,
         files: request.files
diff --git a/test/warning.test.ts b/test/warning.test.ts
index 0d34ea8..b353899 100644
--- a/test/warning.test.ts
+++ b/test/warning.test.ts
@@ -1,6 +1,6 @@
 import Fastify from 'fastify'
 import * as fs from 'fs'
-import { AddressInfo } from 'net'
+import { type AddressInfo } from 'net'
 import * as path from 'path'
 import t from 'tap'
 import FastifyFormidable from '../lib'
@@ -26,7 +26,7 @@ t.test('warning', function (t) {
       removeFilesFromBody: true
     })
 
-    fastify.post<{ Body: { foo: String, file: string } }>('/', {
+    fastify.post<{ Body: { foo: string, file: string } }>('/', {
       onRequest (request, _, done) {
         request.log = {
           warn (msg: string) {