[j-nsp] Setting PE-4FE-TX port to 10m gives 'Illegal media change: invalid speed'

[Ras]

I've just tried to set a port on an PE-4FE-TX to 10m (set interfaces
fe-0/0/1 speed 10m). This works fine on our PE-12FE-TX and the 'commit
check' says all is well, but when I commit I get:

/kernel: %KERN-2: fe-0/0/1: Illegal media change: invalid speed

Are these 100m only ports? If not, what else might be wrong?

Thanks,
Ras