I found this solution that worked for me.

First, create file /etc/systemd/system/lock.service as root:

[Unit]

Description="Make extra sure to lock the screen when suspending"



[Service]

Type=oneshot

User=root

ExecStart=/bin/loginctl lock-sessions



[Install]

WantedBy=suspend.target

Then, in order to to update system configuration, ​type in console:

sudo systemctl daemon-reload

sudo systemctl enable lock.service