diff --git a/src/pocketmine/level/format/SubChunk.php b/src/pocketmine/level/format/SubChunk.php
index 8ee9a118e..08d0ff5b7 100644
--- a/src/pocketmine/level/format/SubChunk.php
+++ b/src/pocketmine/level/format/SubChunk.php
@@ -23,11 +23,9 @@ declare(strict_types=1);
 
 namespace pocketmine\level\format;
 
-$name = __NAMESPACE__ . '\ZERO_NIBBLE_ARRAY';
-if(!defined($name)){
-	define($name, str_repeat("\x00", 2048));
+if(!defined(__NAMESPACE__ . '\ZERO_NIBBLE_ARRAY')){
+	define(__NAMESPACE__ . '\ZERO_NIBBLE_ARRAY', str_repeat("\x00", 2048));
 }
-unset($name);
 
 class SubChunk implements SubChunkInterface{
 	protected $ids;