diff --git a/src/main/java/appeng/container/implementations/ContainerCellWorkbench.java b/src/main/java/appeng/container/implementations/ContainerCellWorkbench.java
index 3b213f551..28659bd80 100644
--- a/src/main/java/appeng/container/implementations/ContainerCellWorkbench.java
+++ b/src/main/java/appeng/container/implementations/ContainerCellWorkbench.java
@@ -55,7 +55,7 @@ public class ContainerCellWorkbench extends ContainerUpgradeable
 	private final AppEngNullInventory nullInventory = new AppEngNullInventory();
 	@GuiSync( 2 )
 	public CopyMode copyMode = CopyMode.CLEAR_ON_REMOVE;
-	private ItemStack prevStack = null;
+	private ItemStack prevStack = ItemStack.EMPTY;
 	private int lastUpgrades = 0;
 
 	public ContainerCellWorkbench( final InventoryPlayer ip, final TileCellWorkbench te )