Confusion in settings block after routers

[Xe]

This code doesn't work:

import asyncdispatch, jester

router api:
  get "/":
    resp Http200, "hi"

settings:
  port = Port(9001)

routes:
  extend api, "/api"

but this code does:

import asyncdispatch, jester

settings:
  port = Port(9001)

router api:
  get "/":
    resp Http200, "hi"

routes:
  extend api, "/api"