diff --git a/src/pocketmine/level/generator/Flat.php b/src/pocketmine/level/generator/Flat.php
index 8478250c4..006d8f385 100644
--- a/src/pocketmine/level/generator/Flat.php
+++ b/src/pocketmine/level/generator/Flat.php
@@ -37,7 +37,14 @@ class Flat extends Generator{
 	private $chunk;
 	/** @var Populator[] */
 	private $populators = [];
-	private $structure, $chunks, $options, $floorLevel, $preset;
+	/** @var int[][] */
+	private $structure;
+	/** @var int */
+	private $floorLevel;
+	/** @var mixed[] */
+	private $options;
+	/** @var string */
+	private $preset;
 
 	public function getSettings() : array{
 		return $this->options;
@@ -92,8 +99,6 @@ class Flat extends Generator{
 		$options = (string) ($preset[3] ?? "");
 		$this->structure = self::parseLayers($blocks);
 
-		$this->chunks = [];
-
 		$this->floorLevel = $y = count($this->structure);
 
 		$this->chunk = new Chunk(0, 0);