/setworldspawn crashes the game when quitting the world

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Can't reproduce, /setworldspawn works fine.

EDIT: After going outwards a few chunks, that so the new world spawn chunks unload, the client freezes upon attempting to exit the world. If you don't quit, there is severe server lag.
i.e: Mobs don't despawn in peaceful and appear to have NoAI:1b set.