diff --git a/src/pocketmine/level/generator/Flat.php b/src/pocketmine/level/generator/Flat.php
index 006d8f385..e738baecf 100644
--- a/src/pocketmine/level/generator/Flat.php
+++ b/src/pocketmine/level/generator/Flat.php
@@ -141,7 +141,7 @@ class Flat extends Generator{
 		}
 	}
 
-	public function generateChunk(int $chunkX, int $chunkZ){
+	public function generateChunk(int $chunkX, int $chunkZ) : void{
 		if($this->chunk === null){
 			if(isset($this->options["preset"]) and $this->options["preset"] != ""){
 				$this->generateBaseChunk($this->options["preset"]);
@@ -155,7 +155,7 @@ class Flat extends Generator{
 		$this->level->setChunk($chunkX, $chunkZ, $chunk);
 	}
 
-	public function populateChunk(int $chunkX, int $chunkZ){
+	public function populateChunk(int $chunkX, int $chunkZ) : void{
 		$this->random->setSeed(0xdeadbeef ^ ($chunkX << 8) ^ $chunkZ ^ $this->level->getSeed());
 		foreach($this->populators as $populator){
 			$populator->populate($this->level, $chunkX, $chunkZ, $this->random);
diff --git a/src/pocketmine/level/generator/Generator.php b/src/pocketmine/level/generator/Generator.php
index e1d4dce21..44b47d90d 100644
--- a/src/pocketmine/level/generator/Generator.php
+++ b/src/pocketmine/level/generator/Generator.php
@@ -60,14 +60,14 @@ abstract class Generator{
 	abstract public function __construct(array $settings = []);
 
 
-	public function init(ChunkManager $level, Random $random){
+	public function init(ChunkManager $level, Random $random) : void{
 		$this->level = $level;
 		$this->random = $random;
 	}
 
-	abstract public function generateChunk(int $chunkX, int $chunkZ);
+	abstract public function generateChunk(int $chunkX, int $chunkZ) : void;
 
-	abstract public function populateChunk(int $chunkX, int $chunkZ);
+	abstract public function populateChunk(int $chunkX, int $chunkZ) : void;
 
 	abstract public function getSettings() : array;
 
diff --git a/src/pocketmine/level/generator/hell/Nether.php b/src/pocketmine/level/generator/hell/Nether.php
index 5ea427804..d4d3eb3a8 100644
--- a/src/pocketmine/level/generator/hell/Nether.php
+++ b/src/pocketmine/level/generator/hell/Nether.php
@@ -62,7 +62,7 @@ class Nether extends Generator{
 		return [];
 	}
 
-	public function init(ChunkManager $level, Random $random){
+	public function init(ChunkManager $level, Random $random) : void{
 		parent::init($level, $random);
 		$this->random->setSeed($this->level->getSeed());
 		$this->noiseBase = new Simplex($this->random, 4, 1 / 4, 1 / 64);
@@ -82,7 +82,7 @@ class Nether extends Generator{
 		$this->populators[] = $ores;*/
 	}
 
-	public function generateChunk(int $chunkX, int $chunkZ){
+	public function generateChunk(int $chunkX, int $chunkZ) : void{
 		$this->random->setSeed(0xdeadbeef ^ ($chunkX << 8) ^ $chunkZ ^ $this->level->getSeed());
 
 		$noise = $this->noiseBase->getFastNoise3D(16, 128, 16, 4, 8, 4, $chunkX * 16, 0, $chunkZ * 16);
@@ -117,7 +117,7 @@ class Nether extends Generator{
 		}
 	}
 
-	public function populateChunk(int $chunkX, int $chunkZ){
+	public function populateChunk(int $chunkX, int $chunkZ) : void{
 		$this->random->setSeed(0xdeadbeef ^ ($chunkX << 8) ^ $chunkZ ^ $this->level->getSeed());
 		foreach($this->populators as $populator){
 			$populator->populate($this->level, $chunkX, $chunkZ, $this->random);
diff --git a/src/pocketmine/level/generator/normal/Normal.php b/src/pocketmine/level/generator/normal/Normal.php
index 0a4692b15..88ddf3619 100644
--- a/src/pocketmine/level/generator/normal/Normal.php
+++ b/src/pocketmine/level/generator/normal/Normal.php
@@ -62,7 +62,7 @@ class Normal extends Generator{
 		}
 	}
 
-	private static function generateKernel(){
+	private static function generateKernel() : void{
 		self::$GAUSSIAN_KERNEL = [];
 
 		$bellSize = 1 / self::$SMOOTH_SIZE;
@@ -87,7 +87,7 @@ class Normal extends Generator{
 		return [];
 	}
 
-	private function pickBiome(int $x, int $z){
+	private function pickBiome(int $x, int $z) : Biome{
 		$hash = $x * 2345803 ^ $z * 9236449 ^ $this->level->getSeed();
 		$hash *= $hash + 223;
 		$xNoise = $hash >> 20 & 3;
@@ -102,7 +102,7 @@ class Normal extends Generator{
 		return $this->selector->pickBiome($x + $xNoise - 1, $z + $zNoise - 1);
 	}
 
-	public function init(ChunkManager $level, Random $random){
+	public function init(ChunkManager $level, Random $random) : void{
 		parent::init($level, $random);
 		$this->random->setSeed($this->level->getSeed());
 		$this->noiseBase = new Simplex($this->random, 4, 1 / 4, 1 / 32);
@@ -177,7 +177,7 @@ class Normal extends Generator{
 		$this->populators[] = $ores;
 	}
 
-	public function generateChunk(int $chunkX, int $chunkZ){
+	public function generateChunk(int $chunkX, int $chunkZ) : void{
 		$this->random->setSeed(0xdeadbeef ^ ($chunkX << 8) ^ $chunkZ ^ $this->level->getSeed());
 
 		$noise = $this->noiseBase->getFastNoise3D(16, 128, 16, 4, 8, 4, $chunkX * 16, 0, $chunkZ * 16);
@@ -244,7 +244,7 @@ class Normal extends Generator{
 		}
 	}
 
-	public function populateChunk(int $chunkX, int $chunkZ){
+	public function populateChunk(int $chunkX, int $chunkZ) : void{
 		$this->random->setSeed(0xdeadbeef ^ ($chunkX << 8) ^ $chunkZ ^ $this->level->getSeed());
 		foreach($this->populators as $populator){
 			$populator->populate($this->level, $chunkX, $chunkZ, $this->random);