Error when using Typescript MongoDb Typings (Cannot find namespace)

i am trying to use mongodb typings which i installed via

npm install @types/mongodb -D

now i want to use the types in a function like that

export default async function insertOne(collection:any, data:any):Promise<MongoClient.Collection.InsertOneWriteOpResult> {
  let db = await state.db
  let col = await db.collection(collection)
  let result = await col.insertOne(data)
  return result
}

i am specifically interested in the Type of InsertOneWriteOpResult. but i am getting the typescript compiler error:

src/utils/mongodb/collection/insert-one.ts|5 col 17 error| Cannot find namespace 'MongoClient'.

i referenced the typings file in my typings.d.ts

/// <reference path="./../node_modules/@types/mongodb/index.d.ts" />

So my question is, which namespace do i have to use to let typescript check against InsertOptionsWriteOpResult?

via divramod