Puppet agent 6.8.0 fails User resources being passed integers for UID and GID

Error: Could not create user xxx: Execution of '[redacted]' returned 1: Error: Could not execute posix command: no implicit conversion of Integer into String

Error: /Stage[main]/Profile::User::Service_account/User[xxx]/ensure: change from 'absent' to 'present' failed: Could not create user xxx: Execution of '[redacted]' returned 1: Error: Could not execute posix command: no implicit conversion of Integer into String (corrective)

  $username     = lookup('user::service_account::username')

  $hiera_uid    = lookup('user::service_account::uid')

  $hiera_gid    = lookup('user::service_account::gid')

  $hiera_home   = lookup('user::service_account::home')

  $hiera_shell  = lookup('user::service_account::shell')

  $hiera_passwd = lookup('user::service_account::passwd')

  # Create the new service account

  group { $username:

    ensure => 'present',

    gid    => $hiera_gid,

    before => User[$username],

  }

  user { $username:

    ensure           => present,

    uid              => $hiera_uid,

    gid              => $hiera_gid,

    home             => $hiera_home,

    shell            => $hiera_shell,

    password         => $hiera_passwd,

    password_max_age => '99999',

    password_min_age => '0',

    require          => Group[$username],

  }

user::service_account::username: xxx

user::service_account::uid: 1234

user::service_account::gid: 1234

user::service_account::home: /home/xxx

user::service_account::shell: /bin/bash