Class[Tajine]: parameter 'webapp' entry 'session_lifetime' expects a String value, got Integer

tajine::webapp:
  default_uri: 'https://tajine.vagrant.example.org/' # used only to generate URLs in a non-HTTP context
  email_from: 'no-reply@vagrant.example.org'
  email_alerting_to: 'sysadmin@vagrant.example.org'
  i18n_default_locale: 'fr' # allowed values: 'en','fr'
  name: 'Vagrant Tajine - Registration authority (RA)'
  shortname: 'Vagrant Tajine (RA)'
  session_lifetime: 1800

Error: Evaluation Error: Error while evaluating a Resource Statement, 
Class[Tajine]: parameter 'webapp' entry 'session_lifetime' 
expects a String value, got Integer 

see: puppet-tajine types/config/webapp.pp vs puppet-comptoir types/config/webapp.pp