Unable to get stack traces when using Lwt.catch

stack_trace.ml

let bar () : unit Lwt.t =
  assert false ;
  Lwt.return_unit

let foo () : unit Lwt.t = bar ()

let run () : unit Lwt.t = foo ()

let run_catch () : unit Lwt.t =
  Lwt.catch run (fun exn ->
      Format.printf
        "@{<error>@{<title>Error@}@}@.  @[<h 0>%a@]@."
        Format.pp_print_text
        (Printexc.to_string exn) ;
      Lwt.return_unit)

let () =
  print_endline "Start" ;
  (* This version doesn't print a stack trace. *)
  Lwt_main.run (run_catch ())
  (* This version does print a stack trace. *)
  (* Lwt_main.run (run ()) *)