IOCaml codemirror

Hello,

I am using the  dev version of Jupyter with the IOcaml kernel.
Every thing works well except that there is no syntax highlighting.
The metadata of the notebook is

{
   "kernelspec": {
     "name": "ocaml",
     "display_name": "OCaml",
     "language": "ocaml"
   },
   "language_info": {
     "version": "4.1.0",
     "name": "ocaml"
   }
}

What should I do to activate codemirror ?

When I add
"codemirror_mode" : "mllike"
in the metadata, this information is removed when the page and reloaded.

Thank you for your help.

Denis Pinsard