diff --git a/src/pocketmine/network/mcpe/protocol/types/NetworkInventoryAction.php b/src/pocketmine/network/mcpe/protocol/types/NetworkInventoryAction.php
index ce2b6b87f..738f6743e 100644
--- a/src/pocketmine/network/mcpe/protocol/types/NetworkInventoryAction.php
+++ b/src/pocketmine/network/mcpe/protocol/types/NetworkInventoryAction.php
@@ -48,8 +48,8 @@ class NetworkInventoryAction{
 	 *
 	 * Expect these to change in the future.
 	 */
-	public const SOURCE_TYPE_CRAFTING_USELESS_MAGIC_NUMBER = -2;
-
+	public const SOURCE_TYPE_CRAFTING_ADD_INGREDIENT = -2;
+	public const SOURCE_TYPE_CRAFTING_REMOVE_INGREDIENT = -3;
 	public const SOURCE_TYPE_CRAFTING_RESULT = -4;
 	public const SOURCE_TYPE_CRAFTING_USE_INGREDIENT = -5;
 
@@ -109,11 +109,6 @@ class NetworkInventoryAction{
 			case self::SOURCE_CREATIVE:
 				break;
 			case self::SOURCE_CRAFTING_GRID:
-				$dummy = $packet->getVarInt();
-				if($dummy !== self::SOURCE_TYPE_CRAFTING_USELESS_MAGIC_NUMBER){
-					throw new \UnexpectedValueException("Useless magic number for crafting-grid type was $dummy, expected " . self::SOURCE_TYPE_CRAFTING_USELESS_MAGIC_NUMBER);
-				}
-				break;
 			case self::SOURCE_TODO:
 				$this->windowId = $packet->getVarInt();
 				switch($this->windowId){
@@ -152,8 +147,6 @@ class NetworkInventoryAction{
 			case self::SOURCE_CREATIVE:
 				break;
 			case self::SOURCE_CRAFTING_GRID:
-				$packet->putVarInt(self::SOURCE_TYPE_CRAFTING_USELESS_MAGIC_NUMBER);
-				break;
 			case self::SOURCE_TODO:
 				$packet->putVarInt($this->windowId);
 				break;
@@ -201,24 +194,16 @@ class NetworkInventoryAction{
 
 				return new CreativeInventoryAction($this->oldItem, $this->newItem, $type);
 			case self::SOURCE_CRAFTING_GRID:
-				return new SlotChangeAction($player->getCraftingGrid(), $this->inventorySlot, $this->oldItem, $this->newItem);
 			case self::SOURCE_TODO:
 				//These types need special handling.
 				switch($this->windowId){
+					case self::SOURCE_TYPE_CRAFTING_ADD_INGREDIENT:
+					case self::SOURCE_TYPE_CRAFTING_REMOVE_INGREDIENT:
+					case self::SOURCE_TYPE_CONTAINER_DROP_CONTENTS: //TODO: this type applies to all fake windows, not just crafting
+						return new SlotChangeAction($player->getCraftingGrid(), $this->inventorySlot, $this->oldItem, $this->newItem);
 					case self::SOURCE_TYPE_CRAFTING_RESULT:
 					case self::SOURCE_TYPE_CRAFTING_USE_INGREDIENT:
 						return null;
-
-					case self::SOURCE_TYPE_CONTAINER_DROP_CONTENTS:
-						//TODO: this type applies to all fake windows, not just crafting
-						$window = $player->getCraftingGrid();
-
-						//DROP_CONTENTS doesn't bother telling us what slot the item is in, so we find it ourselves
-						$inventorySlot = $window->first($this->oldItem, true);
-						if($inventorySlot === -1){
-							throw new \InvalidStateException("Fake container " . get_class($window) . " for " . $player->getName() . " does not contain $this->oldItem");
-						}
-						return new SlotChangeAction($window, $inventorySlot, $this->oldItem, $this->newItem);
 				}
 
 				//TODO: more stuff