Keyboard.presses always returns code 0

[Christian Lawson-Perfect]

I've just been playing in Firefox 58, and Keyboard.presses always produces the KeyCode 0, no matter what key is pressed.
Keyboard.ups produces the right codes.

Here's a small example (on Ellie):

import Html exposing (..)
import Keyboard exposing (KeyCode, presses)


main =
  Html.program
    { init = init
    , view = view
    , update = update
    , subscriptions = subscriptions
    }


-- MODEL


type alias Model = Maybe KeyCode

init : ( Model, Cmd Msg )
init =
  ( Nothing, Cmd.none )



-- UPDATE


type Msg
    = SetCode KeyCode


update : Msg -> Model -> ( Model, Cmd Msg )
update (SetCode code) model = (Just code, Cmd.none)


-- SUBSCRIPTIONS


subscriptions : Model -> Sub Msg
subscriptions model = presses SetCode


-- VIEW


view model = div [] [text <| toString model]