Setting spawnpoint on pressure plates doesn't work

Setting the spawnpoint (with /spawnpoint) on pressure plates and then die will print "Your home bed was missing or obstructed" and send you to the worlds spawn.

What I expected to happen:
Respawn on the pressure plate I set the spawn on

What happend:
I respawned at the worlds spawn with the message "Your home bed was missing or obstructed"

Steps to reproduce:
1. Stand on a pressure plate
2. Type "/spawnpoint"
3. Die (/kill)

Workaround: Set the spawn one block above the pressure plate