diff --git a/index.d.ts b/index.d.ts
index 663b9c5..25c8fc6 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -1,11 +1,8 @@
 /// <reference types="node" />
 
 import {
-  FastifyRequest,
-  RawServerBase,
   FastifyPlugin,
-  FastifyError,
-  FastifyReply
+  preHandlerHookHandler
 } from "fastify";
 
 export interface FastifyHttpProxyOptions {
@@ -14,16 +11,8 @@ export interface FastifyHttpProxyOptions {
   rewritePrefix?: string;
   http2?: boolean;
   proxyPayloads?: boolean;
-  preHandler?: (
-    request: FastifyRequest<RawServerBase>,
-    reply: FastifyReply<RawServerBase>,
-    next: (err?: FastifyError | undefined) => void
-  ) => void;
-  beforeHandler?: (
-    request: FastifyRequest<RawServerBase>,
-    reply: FastifyReply<RawServerBase>,
-    next: (err?: FastifyError | undefined) => void
-  ) => void;
+  preHandler?: preHandlerHookHandler;
+  beforeHandler?: preHandlerHookHandler;
   config?: Object;
   replyOptions?: Object;
 }
diff --git a/package.json b/package.json
index 1b99a04..b9ddca6 100644
--- a/package.json
+++ b/package.json
@@ -4,7 +4,7 @@
   "description": "proxy http requests, for Fastify",
   "main": "index.js",
   "scripts": {
-    "test": "standard | snazzy && tap test/*.js",
+    "test": "standard | snazzy && tap test/*.js && npm run typescript",
     "lint:typescript": "standard --fix --parser @typescript-eslint/parser --plugin typescript test/types/*.ts",
     "typescript": "tsd"
   },
diff --git a/test/index.test-d.ts b/test/index.test-d.ts
index eab0c07..e652a19 100644
--- a/test/index.test-d.ts
+++ b/test/index.test-d.ts
@@ -1,8 +1,6 @@
-import fastify from "fastify";
+import fastify, { RawReplyDefaultExpression, RawRequestDefaultExpression } from "fastify";
 import fastifyHttpProxy from "..";
 import { expectType } from "tsd";
-import { IncomingMessage, ServerResponse } from "http";
-import { Http2ServerRequest, Http2ServerResponse } from "http2";
 
 const app = fastify();
 
@@ -18,11 +16,11 @@ app.register(fastifyHttpProxy, {
   config: { key: 1 },
   replyOptions: { opt: "a" },
   preHandler: (request, reply) => {
-    expectType<IncomingMessage | Http2ServerRequest>(request.raw);
-    expectType<ServerResponse | Http2ServerResponse>(reply.raw);
+    expectType<RawRequestDefaultExpression>(request.raw);
+    expectType<RawReplyDefaultExpression>(reply.raw);
   },
   beforeHandler: (request, reply) => {
-    expectType<IncomingMessage | Http2ServerRequest>(request.raw);
-    expectType<ServerResponse | Http2ServerResponse>(reply.raw);
+    expectType<RawRequestDefaultExpression>(request.raw);
+    expectType<RawReplyDefaultExpression>(reply.raw);
   }
 });