PMMP 4 Undefined constant pocketmine\world\World::HALF_Y_MAX Error

I got this error when joining my PocketMine-MP 4 server:

Code:

[12:22:12.244] [AsyncWorker#0 thread/CRITICAL]: Error: "Undefined constant pocketmine\world\World::HALF_Y_MAX" (EXCEPTION) in "pmsrc/src/world/light/LightUpdate" at line 96
[12:22:12.244] [AsyncWorker#0 thread/CRITICAL]: #0 pmsrc/src/world/light/SkyLightUpdate(154): pocketmine\world\light\LightUpdate->setAndUpdateLight(integer 0, integer 65, integer 0, integer 15)
[12:22:12.244] [AsyncWorker#0 thread/CRITICAL]: #1 pmsrc/src/world/light/LightPopulationTask(69): pocketmine\world\light\SkyLightUpdate->recalculateChunk(integer 0, integer 0)
[12:22:12.244] [AsyncWorker#0 thread/CRITICAL]: #2 pmsrc/src/scheduler/AsyncTask(84): pocketmine\world\light\LightPopulationTask->onRun()
[12:22:12.244] [AsyncWorker#0 thread/CRITICAL]: #3 (): pocketmine\scheduler\AsyncTask->run()
[12:22:12.252] [Server thread/CRITICAL]: Could not execute asynchronous task LightPopulationTask: Task crashed

My server is running on Ubuntu 20.04 LTS and using PMMP 4 PHP 8.0.8 binary. I ran the PreProcessor.php when building the PocketMine-MP from source.

What can I do to fix this error?

 

Are you sure you're using the latest version of PM4?

https://github.com/pmmp/PocketMine-MP/blob/master/src/world/light/LightUpdate.php#L95-L97

 

Yes, of course. I recently cloned the PM4 source from GitHub.