diff --git a/src/pocketmine/Player.php b/src/pocketmine/Player.php
index 05ae682a4..4432a58a2 100644
--- a/src/pocketmine/Player.php
+++ b/src/pocketmine/Player.php
@@ -477,7 +477,7 @@ class Player extends Human implements CommandSender, ChunkLoader, ChunkListener,
 		return $this->lineHeight ?? 7;
 	}
 
-	public function setScreenLineHeight(int $height = null){
+	public function setScreenLineHeight(?int $height){
 		if($height !== null and $height < 1){
 			throw new \InvalidArgumentException("Line height must be at least 1");
 		}
diff --git a/src/pocketmine/command/Command.php b/src/pocketmine/command/Command.php
index 2f47e2029..0cea12cd9 100644
--- a/src/pocketmine/command/Command.php
+++ b/src/pocketmine/command/Command.php
@@ -115,7 +115,7 @@ abstract class Command{
 	/**
 	 * @param string|null $permission
 	 */
-	public function setPermission(string $permission = null){
+	public function setPermission(?string $permission){
 		$this->permission = $permission;
 	}
 
diff --git a/src/pocketmine/command/CommandSender.php b/src/pocketmine/command/CommandSender.php
index 97fed1b29..027a1a5cf 100644
--- a/src/pocketmine/command/CommandSender.php
+++ b/src/pocketmine/command/CommandSender.php
@@ -57,5 +57,5 @@ interface CommandSender extends Permissible{
 	 *
 	 * @param int|null $height
 	 */
-	public function setScreenLineHeight(int $height = null);
+	public function setScreenLineHeight(?int $height);
 }
diff --git a/src/pocketmine/command/ConsoleCommandSender.php b/src/pocketmine/command/ConsoleCommandSender.php
index 32c422a9c..119c55fef 100644
--- a/src/pocketmine/command/ConsoleCommandSender.php
+++ b/src/pocketmine/command/ConsoleCommandSender.php
@@ -142,7 +142,7 @@ class ConsoleCommandSender implements CommandSender{
 		return $this->lineHeight ?? PHP_INT_MAX;
 	}
 
-	public function setScreenLineHeight(int $height = null){
+	public function setScreenLineHeight(?int $height){
 		if($height !== null and $height < 1){
 			throw new \InvalidArgumentException("Line height must be at least 1");
 		}
diff --git a/src/pocketmine/level/ChunkManager.php b/src/pocketmine/level/ChunkManager.php
index 2e669253b..b53996cbc 100644
--- a/src/pocketmine/level/ChunkManager.php
+++ b/src/pocketmine/level/ChunkManager.php
@@ -106,7 +106,7 @@ interface ChunkManager{
 	 * @param int        $chunkZ
 	 * @param Chunk|null $chunk
 	 */
-	public function setChunk(int $chunkX, int $chunkZ, Chunk $chunk = null);
+	public function setChunk(int $chunkX, int $chunkZ, ?Chunk $chunk);
 
 	/**
 	 * Returns the height of the world
diff --git a/src/pocketmine/level/Level.php b/src/pocketmine/level/Level.php
index cb465faef..61b5cb868 100644
--- a/src/pocketmine/level/Level.php
+++ b/src/pocketmine/level/Level.php
@@ -2303,7 +2303,7 @@ class Level implements ChunkManager, Metadatable{
 	 * @param Chunk|null $chunk
 	 * @param bool       $deleteEntitiesAndTiles Whether to delete entities and tiles on the old chunk, or transfer them to the new one
 	 */
-	public function setChunk(int $chunkX, int $chunkZ, Chunk $chunk = null, bool $deleteEntitiesAndTiles = true){
+	public function setChunk(int $chunkX, int $chunkZ, ?Chunk $chunk, bool $deleteEntitiesAndTiles = true){
 		if($chunk === null){
 			return;
 		}
diff --git a/src/pocketmine/level/Position.php b/src/pocketmine/level/Position.php
index 0be7137a9..b1de803ae 100644
--- a/src/pocketmine/level/Position.php
+++ b/src/pocketmine/level/Position.php
@@ -79,7 +79,7 @@ class Position extends Vector3{
 	 *
 	 * @throws \InvalidArgumentException if the specified Level has been closed
 	 */
-	public function setLevel(Level $level = null){
+	public function setLevel(?Level $level){
 		if($level !== null and $level->isClosed()){
 			throw new \InvalidArgumentException("Specified world has been unloaded and cannot be used");
 		}
diff --git a/src/pocketmine/level/SimpleChunkManager.php b/src/pocketmine/level/SimpleChunkManager.php
index 93512944d..a51452cef 100644
--- a/src/pocketmine/level/SimpleChunkManager.php
+++ b/src/pocketmine/level/SimpleChunkManager.php
@@ -102,7 +102,7 @@ class SimpleChunkManager implements ChunkManager{
 	 * @param int        $chunkZ
 	 * @param Chunk|null $chunk
 	 */
-	public function setChunk(int $chunkX, int $chunkZ, Chunk $chunk = null){
+	public function setChunk(int $chunkX, int $chunkZ, ?Chunk $chunk){
 		if($chunk === null){
 			unset($this->chunks[Level::chunkHash($chunkX, $chunkZ)]);
 			return;
diff --git a/src/pocketmine/level/format/Chunk.php b/src/pocketmine/level/format/Chunk.php
index 38799b060..9939cc59d 100644
--- a/src/pocketmine/level/format/Chunk.php
+++ b/src/pocketmine/level/format/Chunk.php
@@ -696,7 +696,7 @@ class Chunk{
 	 *
 	 * @return bool
 	 */
-	public function setSubChunk(int $y, SubChunkInterface $subChunk = null, bool $allowEmpty = false) : bool{
+	public function setSubChunk(int $y, ?SubChunkInterface $subChunk, bool $allowEmpty = false) : bool{
 		if($y < 0 or $y >= $this->height){
 			return false;
 		}
diff --git a/src/pocketmine/permission/BanEntry.php b/src/pocketmine/permission/BanEntry.php
index 80aae0c6e..cb64d7e7c 100644
--- a/src/pocketmine/permission/BanEntry.php
+++ b/src/pocketmine/permission/BanEntry.php
@@ -90,7 +90,7 @@ class BanEntry{
 	 * @param \DateTime|null $date
 	 * @throws \InvalidArgumentException
 	 */
-	public function setExpires(\DateTime $date = null){
+	public function setExpires(?\DateTime $date){
 		if($date !== null){
 			self::validateDate($date);
 		}
diff --git a/src/pocketmine/permission/PermissionAttachmentInfo.php b/src/pocketmine/permission/PermissionAttachmentInfo.php
index 198f21bbf..418edfb81 100644
--- a/src/pocketmine/permission/PermissionAttachmentInfo.php
+++ b/src/pocketmine/permission/PermissionAttachmentInfo.php
@@ -45,7 +45,7 @@ class PermissionAttachmentInfo{
 	 *
 	 * @throws \InvalidStateException
 	 */
-	public function __construct(Permissible $permissible, string $permission, PermissionAttachment $attachment = null, bool $value){
+	public function __construct(Permissible $permissible, string $permission, ?PermissionAttachment $attachment, bool $value){
 		$this->permissible = $permissible;
 		$this->permission = $permission;
 		$this->attachment = $attachment;
diff --git a/src/pocketmine/scheduler/Task.php b/src/pocketmine/scheduler/Task.php
index c5851b587..af7d0c50d 100644
--- a/src/pocketmine/scheduler/Task.php
+++ b/src/pocketmine/scheduler/Task.php
@@ -55,7 +55,7 @@ abstract class Task{
 	/**
 	 * @param TaskHandler|null $taskHandler
 	 */
-	final public function setHandler(TaskHandler $taskHandler = null){
+	final public function setHandler(?TaskHandler $taskHandler){
 		if($this->taskHandler === null or $taskHandler === null){
 			$this->taskHandler = $taskHandler;
 		}
diff --git a/src/pocketmine/tile/ItemFrame.php b/src/pocketmine/tile/ItemFrame.php
index da6d3792f..cd75daeaf 100644
--- a/src/pocketmine/tile/ItemFrame.php
+++ b/src/pocketmine/tile/ItemFrame.php
@@ -68,7 +68,7 @@ class ItemFrame extends Spawnable{
 		return clone $this->item;
 	}
 
-	public function setItem(Item $item = null){
+	public function setItem(?Item $item){
 		if($item !== null and !$item->isNull()){
 			$this->item = clone $item;
 		}else{