User resource with allowdupe executes usermod -o without -u {uid} argument

Puppet Version: 5.4.0
Puppet Server Version: 6.3.0
OS Name/Version: Ubuntu 18.04

I need to ensure a user with the same uid as another existing user but a different name.
Creating the second user is done correctly, but when the second user's password is changed, puppet says it has changed the user's password successfully while in fact it has not changed the password.
Any subsequent runs will also result in puppet reporting a change while actual password is never changed.

Desired Behavior:

When the user already exists the password is changed successfully with the option allowdupe.

Actual Behavior:

puppet code:

# ensure first user

user { 'user1name': 

  ensure   => present,

  uid      => $uid, 

  gid      => $uid,

  home     => $homedir, 

  shell    => $user1[shell], 

  password => $user1[password] 

}

# ensure second user with allowdupe and same uid

user { 'user2name':

  ensure    => present,

  uid       => $uid,

  gid       => $uid,

  allowdupe => true,

  home      => $homedir,

  shell     => $user2[shell],

  password  => $user2[password],

  require   => [File[$homedir], Group[$user2[group]]]

}

Puppet output with --debug flag:

Debug: Executing: '/usr/sbin/usermod -p $6$rounds=5000$viVABC4ghFf32fu7$WynOf/iDV93iipWfANkKAomDTCqBk9IZK/NihhJaeuMuSDrzUVfFqg91/V9lWr2GK1D/E2.bqNJzUpMK2Xest1 -o user2name'
Notice: /Stage[pre]/Xroles::Users::Pre/User[user2name]/password: changed password
Debug: /User[user2name]: The container Class[Xroles::Users::Pre] will propagate my refresh event

Manually executing the usermod command as logged by puppet results in the error: 

usermod: -o flag is only allowed with the -u flag

It seems that the -u flag is missing from the command that is being executed to edit the user password.

Or is it possible that I am declaring my resource(s) in the wrong way?

If there is an issue in the code it will most likely be in:

/lib/puppet/provider/user/useradd.rb