Package posixat

Failed to find a solution:

no platform:
2024-01-29 15:12.25 [INFO] Solving for ocaml-base-compiler, ocaml,
                           posixat using opam_repository_commit 251c5edf2ecdd2541c324dacb931c3606ee71eeb

2024-01-29 15:12.31 [INFO] base: eliminated all possibilities in 2.58 s

2024-01-29 15:12.31 [INFO] = base =

2024-01-29 15:12.31 [INFO] Can't find all required versions.
Selected: base-threads.base base-unix.base jbuilder.transition ocaml-config.3
          posixat&ocaml&ocaml-base-compiler ocaml-base-compiler
          ocaml-base-compiler
- base -> base.v0.9.4
    posixat v0.9.1 requires >= v0.9.4 & < v0.10
- dune -> dune.1.11.4
    jbuilder transition requires < 2.0
- ocaml -> ocaml.4.04.3
    User requested <= 5.1.0
    base v0.9.4 requires >= 4.03.0 & < 4.07.0
    posixat v0.9.1 requires >= 4.03.0 & < 4.05.0
- ocaml-base-compiler -> (problem)
    User requested >= 4.04.1
    Rejected candidates:
      ocaml-base-compiler.5.1.1: Requires ocaml = 5.1.1
      ocaml-base-compiler.5.1.1~rc1: Requires ocaml = 5.1.1
      ocaml-base-compiler.5.1.0: Requires ocaml = 5.1.0
      ocaml-base-compiler.5.1.0~rc3: Requires ocaml = 5.1.0
      ocaml-base-compiler.5.1.0~rc2: Requires ocaml = 5.1.0
      ...
- posixat -> posixat.v0.9.1
    User requested = v0.9.1
- sexplib -> (problem)
    base v0.9.4 requires >= v0.9.3 & < v0.10
    Rejected candidates:
      sexplib.v0.16.0: Incompatible with restriction: >= v0.9.3 & < v0.10
      sexplib.v0.15.1: Incompatible with restriction: >= v0.9.3 & < v0.10
      sexplib.v0.15.0: Incompatible with restriction: >= v0.9.3 & < v0.10
      sexplib.v0.14.0: Incompatible with restriction: >= v0.9.3 & < v0.10
      sexplib.v0.13.0: Incompatible with restriction: >= v0.9.3 & < v0.10
      ...