diff --git a/README.md b/README.md
index d87a2fc2640..bb0c0c6aefd 100644
--- a/README.md
+++ b/README.md
@@ -37,6 +37,7 @@ Additions
 > https://github.com/pmmp/PocketMine-MP/pull/5122
 > https://github.com/pmmp/PocketMine-MP/pull/5232
 > https://github.com/pmmp/PocketMine-MP/pull/5276
+> https://github.com/pmmp/PocketMine-MP/pull/5333
 
 
 ## What is this?
diff --git a/src/inventory/transaction/action/DropItemAction.php b/src/inventory/transaction/action/DropItemAction.php
index 636317fcf71..bf9039b2479 100644
--- a/src/inventory/transaction/action/DropItemAction.php
+++ b/src/inventory/transaction/action/DropItemAction.php
@@ -45,6 +45,9 @@ public function validate(Player $source) : void{
 		if($this->targetItem->getCount() > $this->targetItem->getMaxStackSize()){
 			throw new TransactionValidationException("Target item exceeds item type max stack size");
 		}
+		if($this->targetItem->getLockMode() !== null){
+			throw new TransactionValidationException("Target item is locked in inventory or slot"); // todo I don't think this check is necessary. If the origin item is actually locked in a slot, the SlotChangeAction changing it to air will be invalid anyway.
+		}
 	}
 
 	public function onPreExecute(Player $source) : bool{
diff --git a/src/inventory/transaction/action/SlotChangeAction.php b/src/inventory/transaction/action/SlotChangeAction.php
index 453f0c4d228..f7b3f6687b0 100644
--- a/src/inventory/transaction/action/SlotChangeAction.php
+++ b/src/inventory/transaction/action/SlotChangeAction.php
@@ -27,6 +27,7 @@
 use pocketmine\inventory\transaction\InventoryTransaction;
 use pocketmine\inventory\transaction\TransactionValidationException;
 use pocketmine\item\Item;
+use pocketmine\item\ItemLockMode;
 use pocketmine\player\Player;
 
 /**
@@ -74,6 +75,12 @@ public function validate(Player $source) : void{
 		if($this->targetItem->getCount() > $this->inventory->getMaxStackSize()){
 			throw new TransactionValidationException("Target item exceeds inventory max stack size");
 		}
+		if($this->targetItem->getLockMode()?->equals(ItemLockMode::SLOT()) === true){
+			throw new TransactionValidationException("Target item is locked in slot");
+		}
+		if($this->sourceItem->getLockMode()?->equals(ItemLockMode::SLOT()) === true){
+			throw new TransactionValidationException("Source item is locked in slot");
+		}
 	}
 
 	/**
diff --git a/src/item/Item.php b/src/item/Item.php
index 1a74345b559..ce09c1ac4cf 100644
--- a/src/item/Item.php
+++ b/src/item/Item.php
@@ -47,6 +47,7 @@
 use pocketmine\nbt\tag\StringTag;
 use pocketmine\nbt\TreeRoot;
 use pocketmine\player\Player;
+use pocketmine\utils\AssumptionFailedError;
 use pocketmine\utils\Utils;
 use pocketmine\world\format\io\GlobalItemDataHandlers;
 use function base64_decode;
@@ -66,10 +67,14 @@ class Item implements \JsonSerializable{
 
 	public const TAG_DISPLAY = "display";
 	public const TAG_BLOCK_ENTITY_TAG = "BlockEntityTag";
+	public const TAG_ITEM_LOCK = "minecraft:item_lock";
 
 	public const TAG_DISPLAY_NAME = "Name";
 	public const TAG_DISPLAY_LORE = "Lore";
 
+	public const VALUE_ITEM_LOCK_IN_SLOT = 1;
+	public const VALUE_ITEM_LOCK_IN_INVENTORY = 2;
+
 	public const TAG_KEEP_ON_DEATH = "minecraft:keep_on_death";
 
 	private const TAG_CAN_PLACE_ON = "CanPlaceOn"; //TAG_List<TAG_String>
@@ -98,6 +103,8 @@ class Item implements \JsonSerializable{
 	 */
 	protected array $canDestroy = [];
 
+	protected ?ItemLockMode $lockMode = null;
+
 	protected bool $keepOnDeath = false;
 
 	/**
@@ -227,6 +234,15 @@ public function setCanDestroy(array $canDestroy) : void{
 		}
 	}
 
+	public function getLockMode() : ?ItemLockMode{
+		return $this->lockMode;
+	}
+
+	public function setLockMode(?ItemLockMode $lockMode) : self {
+		$this->lockMode = $lockMode;
+		return $this;
+	}
+
 	/**
 	 * Returns whether players will retain this item on death. If a non-player dies it will be excluded from the drops.
 	 */
@@ -336,6 +352,11 @@ protected function deserializeCompoundTag(CompoundTag $tag) : void{
 				$this->canDestroy[$entry->getValue()] = $entry->getValue();
 			}
 		}
+		$this->lockMode = match ($tag->getByte(self::TAG_ITEM_LOCK, 0)) {
+			self::VALUE_ITEM_LOCK_IN_SLOT => ItemLockMode::SLOT(),
+			self::VALUE_ITEM_LOCK_IN_INVENTORY => ItemLockMode::INVENTORY(),
+			default => null
+		};
 
 		$this->keepOnDeath = $tag->getByte(self::TAG_KEEP_ON_DEATH, 0) !== 0;
 	}
@@ -401,6 +422,16 @@ protected function serializeCompoundTag(CompoundTag $tag) : void{
 			$tag->removeTag(self::TAG_CAN_DESTROY);
 		}
 
+		if ($this->lockMode !== null) {
+			$tag->setByte(self::TAG_ITEM_LOCK, match ($this->lockMode->id()) {
+				ItemLockMode::SLOT()->id() => self::VALUE_ITEM_LOCK_IN_SLOT,
+				ItemLockMode::INVENTORY()->id() => self::VALUE_ITEM_LOCK_IN_INVENTORY,
+				default => throw new AssumptionFailedError("Unknown lock mode")
+			});
+		} else {
+			$tag->removeTag(self::TAG_ITEM_LOCK);
+		}
+
 		if($this->keepOnDeath){
 			$tag->setByte(self::TAG_KEEP_ON_DEATH, 1);
 		}else{
diff --git a/src/item/ItemLockMode.php b/src/item/ItemLockMode.php
new file mode 100644
index 00000000000..991be29011d
--- /dev/null
+++ b/src/item/ItemLockMode.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace pocketmine\item;
+
+use pocketmine\utils\EnumTrait;
+
+/**
+ * This doc-block is generated automatically, do not modify it manually.
+ * This must be regenerated whenever registry members are added, removed or changed.
+ * @see build/generate-registry-annotations.php
+ * @generate-registry-docblock
+ *
+ * @method static ItemLockMode INVENTORY()
+ * @method static ItemLockMode SLOT()
+ */
+final class ItemLockMode{
+	use EnumTrait;
+
+	protected static function setup() : void{
+		self::registerAll(
+			new self("slot"),
+			new self("inventory")
+		);
+	}
+}
\ No newline at end of file
diff --git a/src/world/World.php b/src/world/World.php
index c83743b7e34..1d61e2403e8 100644
--- a/src/world/World.php
+++ b/src/world/World.php
@@ -1920,7 +1920,7 @@ public function getBlockAt(int $x, int $y, int $z, bool $cached = true, bool $ad
 		}
 
 		if($addToCache && $relativeBlockHash !== null){
-			$this->blockCache[$chunkHash][$relativeBlockHash] = $block;
+			$this->blockCache[$chunkHash][$relativeBlockHash] = $block; // todo add fix for https://github.com/pmmp/PocketMine-MP/issues/152 by adding cache size
 		}
 
 		return $block;