diff --git a/src/pocketmine/inventory/AnvilInventory.php b/src/pocketmine/inventory/AnvilInventory.php
index 37490a105..f22b56674 100644
--- a/src/pocketmine/inventory/AnvilInventory.php
+++ b/src/pocketmine/inventory/AnvilInventory.php
@@ -33,17 +33,13 @@ class AnvilInventory extends ContainerInventory{
 	protected $holder;
 
 	public function __construct(Position $pos){
-		parent::__construct($pos->asPosition());
+		parent::__construct($pos->asPosition(), 2);
 	}
 
 	public function getNetworkType() : int{
 		return WindowTypes::ANVIL;
 	}
 
-	public function getDefaultSize() : int{
-		return 2; //1 input, 1 material
-	}
-
 	/**
 	 * This override is here for documentation and code completion purposes only.
 	 * @return Position
diff --git a/src/pocketmine/inventory/ArmorInventory.php b/src/pocketmine/inventory/ArmorInventory.php
index ac5154129..39700c51d 100644
--- a/src/pocketmine/inventory/ArmorInventory.php
+++ b/src/pocketmine/inventory/ArmorInventory.php
@@ -43,17 +43,13 @@ class ArmorInventory extends BaseInventory{
 
 	public function __construct(Living $holder){
 		$this->holder = $holder;
-		parent::__construct();
+		parent::__construct(4);
 	}
 
 	public function getHolder() : Living{
 		return $this->holder;
 	}
 
-	public function getDefaultSize() : int{
-		return 4;
-	}
-
 	public function getHelmet() : Item{
 		return $this->getItem(self::SLOT_HEAD);
 	}
diff --git a/src/pocketmine/inventory/BaseInventory.php b/src/pocketmine/inventory/BaseInventory.php
index 5a96002da..73e079875 100644
--- a/src/pocketmine/inventory/BaseInventory.php
+++ b/src/pocketmine/inventory/BaseInventory.php
@@ -49,11 +49,11 @@ abstract class BaseInventory implements Inventory{
 	protected $slotChangeListener;
 
 	/**
-	 * @param Item[] $items
 	 * @param int    $size
+	 * @param Item[] $items
 	 */
-	public function __construct(array $items = [], ?int $size = null){
-		$this->slots = new \SplFixedArray($size ?? $this->getDefaultSize());
+	public function __construct(int $size, array $items = []){
+		$this->slots = new \SplFixedArray($size);
 
 		$this->setContents($items, false);
 	}
@@ -76,8 +76,6 @@ abstract class BaseInventory implements Inventory{
 		$this->slots->setSize($size);
 	}
 
-	abstract public function getDefaultSize() : int;
-
 	public function getMaxStackSize() : int{
 		return $this->maxStackSize;
 	}
diff --git a/src/pocketmine/inventory/ChestInventory.php b/src/pocketmine/inventory/ChestInventory.php
index cbf63df12..dc4fa69f4 100644
--- a/src/pocketmine/inventory/ChestInventory.php
+++ b/src/pocketmine/inventory/ChestInventory.php
@@ -39,17 +39,13 @@ class ChestInventory extends ContainerInventory{
 	 * @param Chest $tile
 	 */
 	public function __construct(Chest $tile){
-		parent::__construct($tile);
+		parent::__construct($tile, 27);
 	}
 
 	public function getNetworkType() : int{
 		return WindowTypes::CONTAINER;
 	}
 
-	public function getDefaultSize() : int{
-		return 27;
-	}
-
 	/**
 	 * This override is here for documentation and code completion purposes only.
 	 * @return Chest
diff --git a/src/pocketmine/inventory/ContainerInventory.php b/src/pocketmine/inventory/ContainerInventory.php
index 4a808ca57..8a41a73a4 100644
--- a/src/pocketmine/inventory/ContainerInventory.php
+++ b/src/pocketmine/inventory/ContainerInventory.php
@@ -33,9 +33,9 @@ abstract class ContainerInventory extends BaseInventory{
 	/** @var Vector3 */
 	protected $holder;
 
-	public function __construct(Vector3 $holder, array $items = [], ?int $size = null){
+	public function __construct(Vector3 $holder, int $size, array $items = []){
 		$this->holder = $holder;
-		parent::__construct($items, $size);
+		parent::__construct($size, $items);
 	}
 
 	protected function onOpen(Player $who) : void{
diff --git a/src/pocketmine/inventory/CraftingGrid.php b/src/pocketmine/inventory/CraftingGrid.php
index 3da867cd5..b15ac65b0 100644
--- a/src/pocketmine/inventory/CraftingGrid.php
+++ b/src/pocketmine/inventory/CraftingGrid.php
@@ -50,17 +50,13 @@ class CraftingGrid extends BaseInventory{
 	public function __construct(Player $holder, int $gridWidth){
 		$this->holder = $holder;
 		$this->gridWidth = $gridWidth;
-		parent::__construct();
+		parent::__construct($this->getGridWidth() ** 2);
 	}
 
 	public function getGridWidth() : int{
 		return $this->gridWidth;
 	}
 
-	public function getDefaultSize() : int{
-		return $this->getGridWidth() ** 2;
-	}
-
 	public function setSize(int $size) : void{
 		throw new \BadMethodCallException("Cannot change the size of a crafting grid");
 	}
diff --git a/src/pocketmine/inventory/DoubleChestInventory.php b/src/pocketmine/inventory/DoubleChestInventory.php
index 06b439551..51a46e8c4 100644
--- a/src/pocketmine/inventory/DoubleChestInventory.php
+++ b/src/pocketmine/inventory/DoubleChestInventory.php
@@ -40,11 +40,7 @@ class DoubleChestInventory extends ChestInventory implements InventoryHolder{
 		$this->left = $left->getRealInventory();
 		$this->right = $right->getRealInventory();
 		$items = array_merge($this->left->getContents(true), $this->right->getContents(true));
-		BaseInventory::__construct($items);
-	}
-
-	public function getDefaultSize() : int{
-		return $this->left->getDefaultSize() + $this->right->getDefaultSize();
+		BaseInventory::__construct($this->left->getSize() + $this->right->getSize(), $items);
 	}
 
 	public function getInventory(){
diff --git a/src/pocketmine/inventory/EnchantInventory.php b/src/pocketmine/inventory/EnchantInventory.php
index 80709f5c9..4d3a6b97f 100644
--- a/src/pocketmine/inventory/EnchantInventory.php
+++ b/src/pocketmine/inventory/EnchantInventory.php
@@ -33,17 +33,13 @@ class EnchantInventory extends ContainerInventory{
 	protected $holder;
 
 	public function __construct(Position $pos){
-		parent::__construct($pos->asPosition());
+		parent::__construct($pos->asPosition(), 2);
 	}
 
 	public function getNetworkType() : int{
 		return WindowTypes::ENCHANTMENT;
 	}
 
-	public function getDefaultSize() : int{
-		return 2; //1 input, 1 lapis
-	}
-
 	/**
 	 * This override is here for documentation and code completion purposes only.
 	 * @return Position
diff --git a/src/pocketmine/inventory/EnderChestInventory.php b/src/pocketmine/inventory/EnderChestInventory.php
index d7605d837..a0fdfe24c 100644
--- a/src/pocketmine/inventory/EnderChestInventory.php
+++ b/src/pocketmine/inventory/EnderChestInventory.php
@@ -34,17 +34,13 @@ class EnderChestInventory extends ChestInventory{
 	protected $holder;
 
 	public function __construct(){
-		ContainerInventory::__construct(new Position());
+		ContainerInventory::__construct(new Position(), 27);
 	}
 
 	public function getNetworkType() : int{
 		return WindowTypes::CONTAINER;
 	}
 
-	public function getDefaultSize() : int{
-		return 27;
-	}
-
 	/**
 	 * Set the holder's position to that of a tile
 	 *
diff --git a/src/pocketmine/inventory/FurnaceInventory.php b/src/pocketmine/inventory/FurnaceInventory.php
index 1418adb47..79a400c06 100644
--- a/src/pocketmine/inventory/FurnaceInventory.php
+++ b/src/pocketmine/inventory/FurnaceInventory.php
@@ -32,17 +32,13 @@ class FurnaceInventory extends ContainerInventory{
 	protected $holder;
 
 	public function __construct(Furnace $tile){
-		parent::__construct($tile);
+		parent::__construct($tile, 3);
 	}
 
 	public function getNetworkType() : int{
 		return WindowTypes::FURNACE;
 	}
 
-	public function getDefaultSize() : int{
-		return 3; //1 input, 1 fuel, 1 output
-	}
-
 	/**
 	 * This override is here for documentation and code completion purposes only.
 	 * @return Furnace
diff --git a/src/pocketmine/inventory/PlayerCursorInventory.php b/src/pocketmine/inventory/PlayerCursorInventory.php
index 4ad1a4050..e760493f2 100644
--- a/src/pocketmine/inventory/PlayerCursorInventory.php
+++ b/src/pocketmine/inventory/PlayerCursorInventory.php
@@ -31,11 +31,7 @@ class PlayerCursorInventory extends BaseInventory{
 
 	public function __construct(Player $holder){
 		$this->holder = $holder;
-		parent::__construct();
-	}
-
-	public function getDefaultSize() : int{
-		return 1;
+		parent::__construct(1);
 	}
 
 	public function setSize(int $size) : void{
diff --git a/src/pocketmine/inventory/PlayerInventory.php b/src/pocketmine/inventory/PlayerInventory.php
index ff355fad3..df0fedcc2 100644
--- a/src/pocketmine/inventory/PlayerInventory.php
+++ b/src/pocketmine/inventory/PlayerInventory.php
@@ -45,11 +45,7 @@ class PlayerInventory extends BaseInventory{
 	 */
 	public function __construct(Human $player){
 		$this->holder = $player;
-		parent::__construct();
-	}
-
-	public function getDefaultSize() : int{
-		return 36;
+		parent::__construct(36);
 	}
 
 	public function isHotbarSlot(int $slot) : bool{
diff --git a/tests/phpunit/inventory/BaseInventoryTest.php b/tests/phpunit/inventory/BaseInventoryTest.php
index ade55f317..a00bbc1b1 100644
--- a/tests/phpunit/inventory/BaseInventoryTest.php
+++ b/tests/phpunit/inventory/BaseInventoryTest.php
@@ -34,13 +34,8 @@ class BaseInventoryTest extends TestCase{
 	}
 
 	public function testAddItemDifferentUserData() : void{
-		$inv = new class extends BaseInventory{
-			public function getDefaultSize() : int{
-				return 1;
-			}
-			public function getName() : string{
-				return "";
-			}
+		$inv = new class(1) extends BaseInventory{
+
 		};
 		$item1 = ItemFactory::get(Item::ARROW, 0, 1);
 		$item2 = ItemFactory::get(Item::ARROW, 0, 1)->setCustomName("TEST");