try expressions doesn't work inside routes

[alaviss]

import json, jester

routes:
  post "/":
    let input =
      try:
        request.body.parseJson()
      except:
        resp Http400

Got:

test.nim(7, 21) Error: expression 'parseJson(body(request))' is of type 'JsonNode' and has to be discarded

I'm on jester 0.4.3 with nim devel.