utop and printing constructors

When loading up code in utop (or dune utop) and printing any data constructor like Bin.Stop with #show Bin.Stop;; I get a crash.

utop # #show Bin.Stop;;
>> Fatal error: Ident.rename Bin.nat
Fatal error: exception Misc.Fatal_error

~ via  v4.12.0 took 4m41s
❯

While ocaml does not crash. Is this a bug or is there an obvious reason why that would be illegal ?

(* SOTypeLevelNat.ml *)
module Bin : sig
  type stop = Qasdpaokdsap

  type 'a zero = Sasddkasdo

  type 'a one = Zoldjsfoij

  type _ nat =
    | Stop : 'stop nat
    | Times2      : 'n nat -> 'n zero nat
    | Times2Plus1 : 'n nat -> 'n one nat
end = struct
  type stop = Qasdpaokdsap

  type 'a zero = Sasddkasdo

  type 'a one = Zoldjsfoij

  type _ nat =
    | Stop : 'stop nat
    | Times2      : 'n nat -> 'n zero nat
    | Times2Plus1 : 'n nat -> 'n one nat
end

utop # #use  "SOTypeLevelNat.ml";;
module Peano :
  sig
    type 'a s = S
    type z = Z
    type 'n nat = Zero : 'a nat | Succ : 'n nat -> 'n s nat
  end
module Bin :
  sig
    type stop = Qasdpaokdsap
    type 'a zero = Sasddkasdo
    type 'a one = Zoldjsfoij
    type _ nat =
        Stop : 'stop nat
      | Times2 : 'n nat -> 'n zero nat
      | Times2Plus1 : 'n nat -> 'n one nat
  end

printing a type, say, the nat works just fine

utop # #show Bin.nat;;
type nonrec _ nat =
    Stop : 'stop Bin.nat
  | Times2 : 'n Bin.nat -> 'n Bin.zero Bin.nat
  | Times2Plus1 : 'n Bin.nat -> 'n Bin.one Bin.nat