Property 'get' does not exist on type 'FastifyInstance' #1077

You have already researched for similar issues?

I searched for the problem and tried most solutions given without success.

What are you trying to achieve, or the steps to reproduce?

I followed the documentation for installing Fastify with Typescript but I keep getting the type error.

{
  "name": "fst",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "build": "tsc -p tsconfig.json",
    "start": "node ./dist/server.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "fastify": "^5.2.1"
  },
  "devDependencies": {
    "@tsconfig/node18": "^18.2.4",
    "@types/node": "^22.10.5",
    "typescript": "^5.7.2"
  }
}

{
    "extends": "@tsconfig/node18/tsconfig.json",
    "compilerOptions": {
        "outDir": "./dist",
        "lib": ["es2018"],
        "target": "es2018"
    }

}

import fastify from 'fastify'

const server = fastify()

server.get('/ping', async (request, reply) => {
  return 'pong\n'
})

server.listen({ port: 8080 }, (err, address) => {
  if (err) {
    console.error(err)
    process.exit(1)
  }
  console.log(`Server listening at ${address}`)
})


server.listen({port: 3333})

What was the result you received?

Property 'get' does not exist on type 'FastifyInstance<Server<typeof IncomingMessage, typeof ServerResponse>, IncomingMessage, ServerResponse, FastifyBaseLogger, FastifyTypeProviderDefault> & PromiseLike<...> & { ...; }'.ts(2339)

What did you expect?

To not show the error

Context

• node version: 18.19.1
• fastify version: 5.2.1
• os: Ubuntu 24.04.1

I also tried inside Docker with node:23.1-bullseye and I get the same error.