/spawnpoint command doesn't work when used in a command block

I'm working on a new parkour map in an Amplified world, and I am using command blocks to set the player's spawnpoint periodically throughout the map (using the /spawnpoint command within the command block).  However, when I test the command block with /kill, I respawn back at a random block near the world spawn (not where my new spawnpoint is), and I receive the message "Your home bed was missing or obstructed".  /spawnpoint does work if I type the command in chat, but I need it to work using the command block (I am 100% sure that I'm typing it in correctly).  Is there any way that you can fix this?  Thanks!