conf: cookie.expires: Invalid item

Hi,

I'm using Artanis 0.5.1 in Guix System 4716cea.

The configuration file created automatically when you run art create my-project contains an option called cookie.expires. For some reason, that option makes the art work command fail with the following error:

Loading /home/user/my-project/conf/artanis.conf...Backtrace:
In ice-9/boot-9.scm:
  1752:10 10 (with-exception-handler _ _ #:unwind? _ # _)
In unknown file:
           9 (apply-smob/0 #<thunk 7f8ba96c2560>)
In ice-9/boot-9.scm:
    724:2  8 (call-with-prompt _ _ #<procedure default-prompt-handle…>)
In ice-9/eval.scm:
    619:8  7 (_ #(#(#<directory (guile-user) 7f8ba96c5c80>)))
In /gnu/store/99cvihsxnb8y89v5mdy2pjk1qixw7hbj-artanis-0.5.1/bin/.art-real:
    42:12  6 (_ _ _)
In artanis/commands/work.scm:
    141:8  5 (work . _)
In ice-9/boot-9.scm:
   2835:4  4 (save-module-excursion _)
  4380:12  3 (_)
In artanis/artanis.scm:
    218:2  2 (init-server #:statics _ #:cache-statics? _ #:exclude _)
In artanis/config.scm:
   669:11  1 (init-config)
   549:10  0 (parse-namespace-cookie _)

artanis/config.scm:549:10: In procedure parse-namespace-cookie:
#<procedure parse-namespace-cookie (item)> "Config: Invalid item" (expires "3600")

If I comment out that option, art work works.