dnsmasq assigns the same IP address to different hosts

I have a problem with dnsmasq on Arch Linux.
I’ve started a DHCP server using dnsmasq using this configuration:

listen-address=::1,127.0.0.1,10.30.0.1
dhcp-range=10.30.0.2,10.30.0.255,12h

The DHCP server works. It assigns IP addresses in the specified range to hosts, but for some reason it assigns the same IP address for all hosts. I also checked the lease file and it contains only the last connected device.
What is the problem? How can I fix it?
Hope for your help!
Thanks in advance!