src/Tools/Code/code_ml.ML

     (target_OCaml, {serializer = serializer_ocaml, literals = literals_ocaml,
       check = {env_var = "ISABELLE_OCAMLEXEC",
         make_destination = fn p => Path.append p (Path.explode "ROOT.ml")
           (*extension demanded by OCaml compiler*),
         make_command = fn _ =>
-          "\"$ISABELLE_OCAMLFIND\" ocamlopt -w pu -package zarith -linkpkg ROOT.ml"},
+          "\"$ISABELLE_OCAMLFIND\" ocamlopt -w pu -package zarith -linkpkg ROOT.ml </dev/null"},
       evaluation_args = []})
   #> Code_Target.set_printings (Type_Constructor ("fun",
     [(target_SML, SOME (2, fun_syntax)), (target_OCaml, SOME (2, fun_syntax))]))
   #> fold (Code_Target.add_reserved target_SML) ML_Syntax.reserved_names
   #> fold (Code_Target.add_reserved target_SML)