/tmp is sometime cleaned up after snaps are launched

I've come up to a situation where my machine boots, lxd snap is launched :

systemctl status snap.lxd.daemon
● snap.lxd.daemon.service - Service for snap application lxd.daemon
   Loaded: loaded (/etc/systemd/system/snap.lxd.daemon.service; static; vendor preset: enabled)
   Active: active (running) since Mon 2018-11-26 15:31:51 CET; 1h 12min ago

However, I can see this also :

systemctl status systemd-tmpfiles-clean.service
● systemd-tmpfiles-clean.service - Cleanup of Temporary Directories
   Loaded: loaded (/lib/systemd/system/systemd-tmpfiles-clean.service; static; vendor preset: enabled)
   Active: inactive (dead) since Mon 2018-11-26 15:46:46 CET; 55min ago

This situation leads to a folder named after /tmp/snap.${LXD_RANDOM} do be wiped while it is mounted by the snap lxd services... And this causes troubles.

I've come up to try to fix it with creating a /etc/tmpfiles.d/snap.conf file with these two lines :
x /tmp/snap.*
X /tmp/snap.*

I'm not sure this is the right way to prevent the /tmp/snap.${LXD_RANDOM} folder to be erased at all, and don't know whether I'm the only one affected by this bug or not.