diff --git a/src/pocketmine/block/Block.php b/src/pocketmine/block/Block.php
index bdb8871d7..1cfcf5ce1 100644
--- a/src/pocketmine/block/Block.php
+++ b/src/pocketmine/block/Block.php
@@ -111,7 +111,13 @@ class Block extends Position implements BlockIds, Metadatable{
 	 * @return int
 	 */
 	public function getItemId() : int{
-		return $this->itemId ?? $this->getId();
+		if($this->itemId !== null){
+			return $this->itemId;
+		}
+		if($this->id > 255){
+			return 255 - $this->id;
+		}
+		return $this->id;
 	}
 
 	/**
diff --git a/src/pocketmine/block/BlockFactory.php b/src/pocketmine/block/BlockFactory.php
index f8a091ce7..7fc4af2ae 100644
--- a/src/pocketmine/block/BlockFactory.php
+++ b/src/pocketmine/block/BlockFactory.php
@@ -61,14 +61,14 @@ class BlockFactory{
 	 * this if you need to reset the block factory back to its original defaults for whatever reason.
 	 */
 	public static function init() : void{
-		self::$fullList = new \SplFixedArray(4096);
-		self::$getInterceptors = new \SplFixedArray(4096);
+		self::$fullList = new \SplFixedArray(8192);
+		self::$getInterceptors = new \SplFixedArray(8192);
 
-		self::$lightFilter = \SplFixedArray::fromArray(array_fill(0, 256, 1));
-		self::$diffusesSkyLight = \SplFixedArray::fromArray(array_fill(0, 256, false));
-		self::$blastResistance = \SplFixedArray::fromArray(array_fill(0, 256, 0));
+		self::$lightFilter = \SplFixedArray::fromArray(array_fill(0, 512, 1));
+		self::$diffusesSkyLight = \SplFixedArray::fromArray(array_fill(0, 512, false));
+		self::$blastResistance = \SplFixedArray::fromArray(array_fill(0, 512, 0));
 
-		self::$stateMasks = \SplFixedArray::fromArray(array_fill(0, 256, 0));
+		self::$stateMasks = \SplFixedArray::fromArray(array_fill(0, 512, 0));
 
 		self::registerBlock(new Air());
 
diff --git a/src/pocketmine/item/ItemBlock.php b/src/pocketmine/item/ItemBlock.php
index 4fa540b14..da455e517 100644
--- a/src/pocketmine/item/ItemBlock.php
+++ b/src/pocketmine/item/ItemBlock.php
@@ -39,8 +39,15 @@ class ItemBlock extends Item{
 	 * @param int|null $itemId
 	 */
 	public function __construct(int $blockId, int $meta = 0, int $itemId = null){
+		if($blockId < 0){ //extended blocks
+			if($itemId === null){
+				$itemId = $blockId;
+			}
+			$blockId = 255 - $blockId;
+		}
 		$this->blockId = $blockId;
 		$this->setDamage($meta);
+
 		parent::__construct($itemId ?? $blockId, $meta, $this->getBlock()->getName());
 	}