I can't unmask a service on Kubuntu Wily 15.10

I'm using Kubuntu Wily 15.10 (fully upgraded). It already had installed the cryptsetup package.

I'm trying to start the cryptdisks service but I get this:

$ sudo service cryptdisks start
Failed to start cryptdisks.service: Unit cryptdisks.service is masked.

And yes, it's masked.

$ sudo systemctl list-unit-files | grep cryptdisks
cryptdisks-early.service                   masked  
cryptdisks.service                         masked  

If I try to unmask the service, nothing happens.

$ sudo systemctl unmask cryptdisks-early.service 
$ sudo systemctl unmask cryptdisks.service 
$ sudo systemctl list-unit-files | grep cryptdisks
cryptdisks-early.service                   masked  
cryptdisks.service                         masked  

Take note that systemctl unmask does not return anything. What can I do?

Check if you have a symlink /etc/systemd/system/cryptdisks.service or /lib/systemd/system/cryptdisks.service to /dev/null. If so, delete the symlink manually.

And also for cryptdisks-early.service.

After that:

sudo apt-get remove cryptsetup
sudo apt-get install cryptsetup