diff --git a/src/inventory/CallbackInventoryChangeListener.php b/src/inventory/CallbackInventoryChangeListener.php
index 0978060c4..e16e01501 100644
--- a/src/inventory/CallbackInventoryChangeListener.php
+++ b/src/inventory/CallbackInventoryChangeListener.php
@@ -46,7 +46,7 @@ class CallbackInventoryChangeListener implements InventoryChangeListener{
 	 */
 	public function __construct(?\Closure $onSlotChange, ?\Closure $onContentChange){
 		if($onSlotChange !== null){
-			Utils::validateCallableSignature(function(Inventory	$inventory, int $slot){}, $onSlotChange);
+			Utils::validateCallableSignature(function(Inventory $inventory, int $slot){}, $onSlotChange);
 		}
 		if($onContentChange !== null){
 			Utils::validateCallableSignature(function(Inventory $inventory){}, $onContentChange);