Cannot bundle anything for ocaml-4.12.0

[UnixJunkie]

# opam-bundle minicli
No OCaml version selected, will use 4.12.0.
No environment specified, will use the following for package resolution (based
on the host system):
  - arch = "x86_64"
  - os = "linux"
  - os-distribution = "ubuntu"
  - os-version = "20.04"
  - os-family = "debian"

<><> Initialising repositories ><><><><><><><><><><><><><><><><><><><><><><><><>
[opam.ocaml.org] Initialised

<><> Resolving package set ><><><><><><><><><><><><><><><><><><><><><><><><><><>
[ERROR] No solution for minicli & ocaml-bootstrap.4.12.0: The following
        dependencies couldn't be met:
          - ocaml-bootstrap -> ocaml -> ocaml-config >= 2 ->
        ocaml-base-compiler >=
            4.12.0~ -> ocaml-beta
              unmet availability conditions: enable-ocaml-beta-repository
          - ocaml-bootstrap -> ocaml -> ocaml-config >= 2 ->
        ocaml-base-compiler >=
            4.12.0~ -> ocaml >= 4.13.0
              no matching version
        Your request can't be satisfied:
          - ocaml-bootstrap is in conflict with ocaml-base-compiler

minicli is just an example (pure ocaml code, not dependencies)

[UnixJunkie]

pinning the development version works