TypeError: Cannot read property 'name' of undefined

[capaj]

I wanted to try this out and with the code:

import {
  Type,
  Field,
  Mutation,
  String,
  Boolean,
  Int,
  makeSchema
} from 'graphql-typescript'

@Type class Query {
  constructor() {
    this.box = new Size()
  }
  @Field box : Size
}

@Type class Size {
  @Field height : Int = 0
  @Field width : Int = 0
  @Field length : Int = 0
}

const schema = makeSchema(Query, {types: [Size]})

console.log(schema)

I am getting this error:

TypeError: Cannot read property 'name' of undefined
    at Object.createProperty (/home/capaj/git_projects/graphql/gql-ts-sample-project/node_modules/graphql-typescript/src/services.ts:11:26)
    at Field (/home/capaj/git_projects/graphql/gql-ts-sample-project/node_modules/graphql-typescript/src/decorators/Field.ts:45:19)
    at DecorateProperty (/home/capaj/git_projects/graphql/gql-ts-sample-project/node_modules/reflect-metadata/Reflect.ts:1214:35)
    at Object.decorate (/home/capaj/git_projects/graphql/gql-ts-sample-project/node_modules/reflect-metadata/Reflect.ts:737:24)
    at __decorate (/home/capaj/git_projects/graphql/gql-ts-sample-project/server.ts:4:92)
    at /home/capaj/git_projects/graphql/gql-ts-sample-project/server.ts:15:10
    at Object.<anonymous> (/home/capaj/git_projects/graphql/gql-ts-sample-project/server.ts:11:7)
    at Module._compile (module.js:635:30)
    at Module.m._compile (/home/capaj/.nvm/versions/node/v8.9.3/lib/node_modules/ts-node/src/index.ts:403:23)
    at Module._extensions..js (module.js:646:10)

[capaj]

oh you have to target ES6 with your typescript compiler! Makes sense.