/spawnpoint/Selector issue without Feedback from the game

I was trying to make a map in the lates Snapshot and was trying to use the /spawnpoint command. I tried it both in a Commandblock aand in the Chat, but it didnt do anything, there was not even an Errormessage. I did not change any Gamerules and played in an empty flatmap. The command i used was /spawnpoint @a[x=1008,y=0,z=0,dx=272,dy=256,dz=272,m=0] 0 31 0. The weird thing is that when I tried /spawnpoint @a 0 31 0, it worked, so it might also be an issue with the selctor, but it should be ixed for the final release, because I also didnt got an errormessage as i mentioned, it just did not do anything. The two screenshots were created before and after i ran the command.