RESTful JSON API using Eliom example not working

[MikkelStorgaard]

I'm on
Ocaml 4.07.1
ppx_deriving_yojson 3.5.1
ppx_deriving 4.4
yojson 1.7.0
eliom 6.7.0

It seems like ppx_deriving_yojson is generating an extra function with the name _, for the last of the derived types.
Am I doing something wrong?

trading_model.eliom:
[%%shared
type sellOrderCapture = {
  sellOrderId : int;
}
[@@deriving yojson]
 
type buyOrderCapture = {
  buyOrderId : int;
  quantity : int;
}
[@@deriving yojson]
 
type t = {
  sellOrder : sellOrderCapture;
  buyOrders : buyOrderCapture list;
}
[@@deriving yojson]
 
Error:
File "_server/trading_model.type_mli", line 17, characters 8-9:
Error: Syntax error
 
 
trading_model.type_mli:
module MatchCapture :
sig
  type sellOrderCapture = { sellOrderId : int; }
  val sellOrderCapture_to_yojson : sellOrderCapture -> Yojson.Safe.t
  val sellOrderCapture_of_yojson :
    Yojson.Safe.t -> sellOrderCapture Ppx_deriving_yojson_runtime.error_or
  type buyOrderCapture = { buyOrderId : int; quantity : int; }
  val buyOrderCapture_to_yojson : buyOrderCapture -> Yojson.Safe.t
  val buyOrderCapture_of_yojson :
    Yojson.Safe.t -> buyOrderCapture Ppx_deriving_yojson_runtime.error_or
  type t = {
    sellOrder : sellOrderCapture;
    buyOrders : buyOrderCapture list;
  }
  val to_yojson : t -> Yojson.Safe.t
  val of_yojson : Yojson.Safe.t -> t Ppx_deriving_yojson_runtime.error_or
  val _ : Yojson.Safe.t -> t Ppx_deriving_yojson_runtime.error_or
end

[balat]

No idea about this one. Is this fixed?