Command block spawn point

I'm creator of adventure maps and releasing 1.8 has ruined most of my maps. Problem is that /spawnpoint @a in a command block is not working anymore.
It's says it needs to add coordinates to work. But in last versions it was working like when you powered up command block with /spawnpoint @a it set your spawnpoint as your current coordinations without having to write 'em into the command. Please fix this. My maps doesn't work.

Thanks.