diff --git a/src/pocketmine/level/format/Chunk.php b/src/pocketmine/level/format/Chunk.php
index 27892f8fb..05bfca2ce 100644
--- a/src/pocketmine/level/format/Chunk.php
+++ b/src/pocketmine/level/format/Chunk.php
@@ -840,8 +840,12 @@ class Chunk{
 	 */
 	public function collectGarbage() : void{
 		foreach($this->subChunks as $y => $subChunk){
-			if(!($subChunk instanceof EmptySubChunk) and $subChunk->isEmpty()){ //normal subchunk full of air, remove it and replace it with an empty stub
-				$this->subChunks[$y] = $this->emptySubChunk;
+			if($subChunk instanceof SubChunk){
+				if($subChunk->isEmpty()){
+					$this->subChunks[$y] = $this->emptySubChunk;
+				}else{
+					$subChunk->collectGarbage();
+				}
 			}
 		}
 	}
diff --git a/src/pocketmine/level/format/SubChunk.php b/src/pocketmine/level/format/SubChunk.php
index 6dc8db096..a0c811b4f 100644
--- a/src/pocketmine/level/format/SubChunk.php
+++ b/src/pocketmine/level/format/SubChunk.php
@@ -23,8 +23,9 @@ declare(strict_types=1);
 
 namespace pocketmine\level\format;
 
-class SubChunk implements SubChunkInterface{
+define(__NAMESPACE__ . '\ZERO_NIBBLE_ARRAY', str_repeat("\x00", 2048));
 
+class SubChunk implements SubChunkInterface{
 	protected $ids;
 	protected $data;
 	protected $blockLight;
@@ -44,6 +45,7 @@ class SubChunk implements SubChunkInterface{
 		self::assignData($this->data, $data, 2048);
 		self::assignData($this->skyLight, $skyLight, 2048, "\xff");
 		self::assignData($this->blockLight, $blockLight, 2048);
+		$this->collectGarbage();
 	}
 
 	public function isEmpty(bool $checkLight = true) : bool{
@@ -51,7 +53,7 @@ class SubChunk implements SubChunkInterface{
 			substr_count($this->ids, "\x00") === 4096 and
 			(!$checkLight or (
 				substr_count($this->skyLight, "\xff") === 2048 and
-				substr_count($this->blockLight, "\x00") === 2048
+				$this->blockLight === ZERO_NIBBLE_ARRAY
 			))
 		);
 	}
@@ -203,4 +205,21 @@ class SubChunk implements SubChunkInterface{
 	public function __debugInfo(){
 		return [];
 	}
+
+	public function collectGarbage() : void{
+		/*
+		 * This strange looking code is designed to exploit PHP's copy-on-write behaviour. Assigning will copy a
+		 * reference to the const instead of duplicating the whole string. The string will only be duplicated when
+		 * modified, which is perfect for this purpose.
+		 */
+		if($this->data === ZERO_NIBBLE_ARRAY){
+			$this->data = ZERO_NIBBLE_ARRAY;
+		}
+		if($this->skyLight === ZERO_NIBBLE_ARRAY){
+			$this->skyLight = ZERO_NIBBLE_ARRAY;
+		}
+		if($this->blockLight === ZERO_NIBBLE_ARRAY){
+			$this->blockLight = ZERO_NIBBLE_ARRAY;
+		}
+	}
 }