Hi guix !

I'm trying to config a mcron service type for mbsync, something 
simple, but there are few example on the web for the new 
home-mcron-service-type. I try something like this :

(use-modules (gnu packages mail)
             (gnu packages tls)
             (gnu home services mcron))


(define update-mail-service
  #~(job '(next-minute '(range 0 60 5))
         (lambda ()
           (execl (string-append #$isync "/bin/mbsync")
                  "mbync"
                  "-a"))
         "fetch mail"))

(define-public %mail-module
  (home-module
   (list mu
         isync
         imapfilter
         msmtp
         gnutls)

   (list
    (simple-service 'isync-mail-config-service
                    home-files-service-type
                    `(
                      (".mbsyncrc" ,(local-file 
                      "../config/mail/mbsyncrc"))
                      (".msmtprc",(local-file 
                      "../config/mail/msmtprc"))
                      (".imapfilter/config.lua",(local-file 
                      "../config/mail/config.lua"))))
    (simple-service `mcron-mail-update-service
                    home-mcron-service-type
                    (list update-mail-service))
        )))

but when i run reconfigure, i have an error in drv compilation :

Backtrace:
           7 (primitive-load 
           "/gnu/store/dpaczpr4j05437bk4dr1snqnfjx9ipfl-mcron-1.2.1/bin/mcron")
In mcron/scripts/mcron.scm:
    103:6  6 (main)
In ice-9/boot-9.scm:
   260:13  5 (for-each #<procedure 7ffff3f343c0 at 
   mcron/scripts/mcron.scm:103:16 (file)> _)
In unknown file:
           4 (eval-string "update-mail-service" #<directory (mcron 
           job-specifier) 7ffff4035780>)
In ice-9/boot-9.scm:
   2835:4  3 (save-module-excursion #<procedure 7ffff2a51980 at 
   ice-9/eval-string.scm:66:9 ()>)
In ice-9/eval-string.scm:
     38:6  2 (read-and-eval #<input: string 7ffff2db78c0> #:lang 
     _)
In ice-9/eval.scm:
   223:20  1 (proc #<directory (mcron job-specifier) 
   7ffff4035780>)
In unknown file:
           0 (%resolve-variable (7 . update-mail-service) 
           #<directory (mcron job-specifier) 7ffff4035780>)

ERROR: In procedure %resolve-variable:
Unbound variable: update-mail-service
Backtrace:
           2 (primitive-load 
           "/gnu/store/b3k8pm2gabw29rmb86r5j4j4jzz7847d-mcron-job-builder")
In ice-9/eval.scm:
    619:8  1 (_ #f)
In guix/build/utils.scm:
    762:6  0 (invoke 
    "/gnu/store/dpaczpr4j05437bk4dr1snqnfjx9ipfl-mcron-1.2.1/bin/mcron" 
    "--schedule=20" "prologue" "job")

guix/build/utils.scm:762:6: In procedure invoke:
ERROR:
  1. &invoke-error:
      program: 
      "/gnu/store/dpaczpr4j05437bk4dr1snqnfjx9ipfl-mcron-1.2.1/bin/mcron"
      arguments: ("--schedule=20" "prologue" "job")
      exit-status: 1
      term-signal: #f
      stop-signal: #f

Any help appreciated :) !
Best regards,