TS-451+: error no such partition

I want to reflash my NAS, but the instructions only include an image for TS-451S. Is this a safe image for my TS-451+?

Symptoms

My TS-451+ passes POST (1 beep after ~5s). Given that I pass POST, I assume I haven’t encountered lpc death?
Then I see the error “error no such partition”
And I’m dropped into a grub shell.

There is an image for Ts-x51+ right here

https://eu1.qnap.com/Storage/tsd/fullimage/F_TS-X51_20150605-1.3.0.img

D’oh!
Thanks