ocsigen-start is broken with a clash

[Denommus]

It's working in nixpkgs, but in nix-ocaml overlay it gives the error:

Error: Conflict between the following libraries:
- "ocsigenserver.http" in _build/default/src/http
- "http" in
  /nix/store/bijqmv8ma263swyxvsg46yg7qvwsfrnw-ocaml5.2.0-http-n-a/lib/ocaml/5.2.0/site-lib/http
  -> required by library "cohttp-lwt-unix" in
     /nix/store/qgcxr7sk62b3lw4kjk0daamhs7wmvjr7-ocaml5.2.0-cohttp-lwt-unix-n-a/lib/ocaml/5.2.0/site-lib/cohttp-lwt-unix
  -> required by library "ocsigenserver" in _build/default/src/server
-> required by executable ocsigenserver in src/dune:2
-> required by _build/default/src/ocsigenserver.bc
-> required by _build/install/default/bin/ocsigenserver
-> required by _build/default/ocsigenserver.install
-> required by alias install
Done: 61% (8/13, 5 left) (jobs: 0)^M                                  ^MDone: 61% (8/13, 5 left) (jobs: 0)^M             
                     ^MDone: 52% (9/17, 8 left, 1 failed) (jobs: 0)^M                                            ^MDone: 
6% (16/233, 217 left, 1 failed) (jobs: 0)^M                                               ^MError: Conflict between the f
ollowing libraries:                                                                                                     
- "ocsigenserver.http" in _build/default/src/http
- "http" in
  /nix/store/bijqmv8ma263swyxvsg46yg7qvwsfrnw-ocaml5.2.0-http-n-a/lib/ocaml/5.2.0/site-lib/http
  -> required by library "cohttp-lwt-unix" in
     /nix/store/qgcxr7sk62b3lw4kjk0daamhs7wmvjr7-ocaml5.2.0-cohttp-lwt-unix-n-a/lib/ocaml/5.2.0/site-lib/cohttp-lwt-unix
-> required by
   _build/default/src/server/.ocsigenserver.objs/native/ocsigen_cohttp.cmx
-> required by _build/install/default/lib/ocsigenserver/ocsigen_cohttp.cmx
-> required by _build/default/ocsigenserver.install
-> required by alias install

[anmonteiro]

Guess it won’t be supported until it gets Cohttp 6 compatibility