Cannot use "hpet" as clock source for qemu guest

Issue

hpet clock source is available on the host:

# cat /sys/devices/system/clocksource/clocksource0/available_clocksource
tsc hpet acpi_pm 

It is also configured in guest libvirt xml:

      <clock offset='localtime'>
        <timer name='hpet' present='yes'/>
      </clock>

But it's not available on the guest:

# cat /sys/devices/system/clocksource/clocksource0/available_clocksource 
kvm-clock tsc acpi_pm