diff --git a/src/pocketmine/level/SimpleChunkManager.php b/src/pocketmine/level/SimpleChunkManager.php
index 7375bd7a6..bd480e9dd 100644
--- a/src/pocketmine/level/SimpleChunkManager.php
+++ b/src/pocketmine/level/SimpleChunkManager.php
@@ -117,6 +117,10 @@ class SimpleChunkManager implements ChunkManager{
 		$this->chunks[Level::chunkHash($chunkX, $chunkZ)] = $chunk;
 	}
 
+	public function cleanChunks(){
+		$this->chunks = [];
+	}
+
 	/**
 	 * Gets the level seed
 	 *
diff --git a/src/pocketmine/level/generator/PopulationTask.php b/src/pocketmine/level/generator/PopulationTask.php
index 5743b02b6..ecd8708cb 100644
--- a/src/pocketmine/level/generator/PopulationTask.php
+++ b/src/pocketmine/level/generator/PopulationTask.php
@@ -127,13 +127,14 @@ class PopulationTask extends AsyncTask{
 				if(!$c->hasChanged()){
 					$chunks[$i] = null;
 				}
-				$manager->setChunk($c->getX(), $c->getZ(), null);
 			}else{
 				//This way non-changed chunks are not set
 				$chunks[$i] = null;
 			}
 		}
 
+		$manager->cleanChunks();
+
 		$this->chunk00 = $chunks[0] !== null ? $chunks[0]->toFastBinary() : null;
 		$this->chunk01 = $chunks[1] !== null ? $chunks[1]->toFastBinary() : null;
 		$this->chunk02 = $chunks[2] !== null ? $chunks[2]->toFastBinary() : null;