Error Problems in module definition

nixy.ml

open Core.Std
open Core_extended.Std
open Async.Std
open Deferred.Result.Monad_infix

module Log = Nixy_log.Make(Nixy_log.Syslog)
module Config = Config.Make(Log)

nixy_log.mli

open Core.Std
open Async.Std

(* This module produces log output that complies with
   [rfc5424](http://tools.ietf.org/html/rfc5424) *)

module type S =
sig
  type t

  type tags = (String.t * String.t) List.t

  type severity =
    | Emergency
    | Alert
    | Critical
    | Error
    | Warning
    | Notice
    | Informational
    | Debug

  val set_msgid: t -> msgid:String.t -> t
  val add_tags: t -> tags:tags -> t
  val flush: t -> Unit.t Deferred.t
  val debug: t -> ?tags:(String.t * String.t) List.t -> ?msgid:String.t
    -> ('a, Unit.t, String.t, Unit.t) format4 -> 'a

  val info: t -> ?tags:(String.t * String.t) List.t
    -> ?msgid:String.t -> ('a, Unit.t, String.t, Unit.t) format4 -> 'a
  val notice: t -> ?tags:(String.t * String.t) List.t
    -> ?msgid:String.t -> ('a, Unit.t, String.t, Unit.t) format4 -> 'a
  val warning: t -> ?tags:(String.t * String.t) List.t
    -> ?msgid:String.t -> ('a, Unit.t, String.t, Unit.t) format4 -> 'a
  val error: t -> ?tags:(String.t * String.t) List.t
    -> ?msgid:String.t -> ('a, Unit.t, String.t, Unit.t) format4 -> 'a
  val critical: t -> ?tags:(String.t * String.t) List.t
    -> ?msgid:String.t -> ('a, Unit.t, String.t, Unit.t) format4 -> 'a
  val alert: t -> ?tags:(String.t * String.t) List.t
    -> ?msgid:String.t -> ('a, Unit.t, String.t, Unit.t) format4 -> 'a
  val emergency:  t -> ?tags:(String.t * String.t) List.t
    -> ?msgid:String.t -> ('a, Unit.t, String.t, Unit.t) format4 -> 'a

end

module type Syslog =
sig
  include S

  type facility =
    | Kernel_messages
    | User_level_messages
    | Mail_system
    | System_daemons
    | Security_authorization_messages_1
    | Messages_generated_internally_by_syslogd
    | Line_printer_subsystem
    | Network_news_subsystem
    | UUCP_subsystem
    | Clock_daemon_1
    | Security_authorization_messages_2
    | FTP_daemon
    | NTP_subsystem
    | Log_audit
    | Log_alert
    | Clock_daemon_2
    | Local_use_0
    | Local_use_1
    | Local_use_2
    | Local_use_3
    | Local_use_4
    | Local_use_5
    | Local_use_6
    | Local_use_7

  val make : facility:facility -> hostname:String.t -> app_name:String.t
    -> ?procid:String.t -> ?tags:tags ->  ?msgid:String.t
    -> ?sdid:String.t -> severity:severity -> Unit.t -> t

  val set_hostname: t -> hostname:String.t -> t
end

module Make(Impl : S) : S with type t = Impl.t

out.txt

make[1]: Entering directory '/Users/ericbmerritt/workspace/nixy'
/Users/ericbmerritt/workspace/nixy/gen-semver.sh lib/version.ml
ocamlbuild -j 2 -build-dir /Users/ericbmerritt/workspace/nixy/_build -use-ocamlfind -cflags -bin-annot -lflags -g nixy.cma nixy.cmx nixy.cmxa nixy.a nixy.cmxs nixy.native
+ ocamlfind ocamlc -c -bin-annot -thread -warn-error A -package async_shell -package jingoo -package cohttp -package cohttp.async -package async_extra -package sexplib.syntax -package fieldslib.syntax -package core -package core_extended -package async -syntax camlp4o -w -40 -I lib -o lib/nixy.cmo lib/nixy.ml
File "lib/nixy.ml", line 6, characters 27-42:
Error: Unbound module Nixy_log.Syslog
Command exited with code 2.
Compilation unsuccessful after building 12 targets (11 cached) in 00:00:00.
Makefile:95: recipe for target 'build' failed
make[1]: *** [build] Error 10
make[1]: Leaving directory '/Users/ericbmerritt/workspace/nixy'