ocaml-src 4.09.0

Error log

The package failed to build. The error log from opam follows.

Opam plugin "depext" may require upgrading/reinstalling. Reinstall the plugin on the current switch? [Y/n] y
The following actions will be performed:
  - recompile ocaml-options-vanilla 1      [upstream or system changes]
  - recompile ocaml-base-compiler   5.1.1* [upstream or system changes]
  - recompile ocaml-config          3      [uses ocaml-base-compiler]
  - recompile ocaml                 5.1.1  [uses ocaml-base-compiler]
  - recompile opam-depext           1.2.3
  - recompile base-domains          base   [uses ocaml]
  - recompile base-nnp              base   [uses base-domains]
===== 7 to recompile =====

<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
-> retrieved ocaml-config.3  (cached)
-> removed   ocaml-options-vanilla.1
-> installed ocaml-options-vanilla.1
-> retrieved ocaml-base-compiler.5.1.1  (cached)
-> retrieved opam-depext.1.2.3  (cached)
-> removed   base-nnp.base
-> removed   base-domains.base
-> removed   opam-depext.1.2.3
-> removed   ocaml.5.1.1
-> removed   ocaml-config.3
-> removed   ocaml-base-compiler.5.1.1
-> installed ocaml-base-compiler.5.1.1
-> installed ocaml-config.3
-> installed ocaml.5.1.1
-> installed base-domains.base
-> installed base-nnp.base
-> installed opam-depext.1.2.3
Done.

<><> opam-depext.1.2.3 installed successfully <><><><><><><><><><><><><><><><><>
=> opam-depext is unnecessary when used with opam >= 2.1. Please use opam install directly instead
# Run eval $(opam env) to update the current shell environment

<><> Carrying on to "opam depext -viy ocaml-src.4.09.0" <><><><><><><><><><><><>

Since version 2.1, opam now handles external dependencies alongside OCaml ones, and the `depext` plugin interface is provided for backwards compatibility only. Consider using your usual `opam install` command to install both OCaml and system dependencies, or `opam install <pkg> --depext-only` if you want to only install external dependencies.
# Detecting depexts using vars: arch=x86_64, os=linux, os-distribution=debian, os-family=debian
[ERROR] No solution for ocaml-src.4.09.0:   * No agreement on the version of ocaml:
            - (invariant) -> ocaml-base-compiler = 5.1.1 -> ocaml = 5.1.1
            - ocaml-src = 4.09.0 -> ocaml = 4.09.0
            You can temporarily relax the switch invariant with `--update-invariant'


Command failed: opam --cli=2.1 list --readonly --external '--resolve=ocaml-src.4.09.0' --color=never returned 20