How to start a service when a device is created under /dev/pts/

[Giuseppe Sacco <giuseppe@xxxxxxxxx>]

Hello,
I am working on hylafax, a program for sending and receiving faxes, and I
am facing a problem when it should wait for a device that is not in /dev/
but in /dev/pts/. It seems that udev events only cover device creation in
/dev/ and are not fired when the device appear in /dev/pts.

This is an excerpt for the unit that works for all serial devices in /dev:

[Unit]
Description=HylaFAX faxgetty %I
BindsTo=dev-%i.device
After=dev-%i.device

Is there any workaround for starting the service unit when the device is
created?

Thank you,
Giuseppe