diff --git a/src/main/scala/li/cil/oc/common/GuiHandler.scala b/src/main/scala/li/cil/oc/common/GuiHandler.scala
index 4b3fd9e9c..c4c6a2c1b 100644
--- a/src/main/scala/li/cil/oc/common/GuiHandler.scala
+++ b/src/main/scala/li/cil/oc/common/GuiHandler.scala
@@ -87,7 +87,7 @@ abstract class GuiHandler extends IGuiHandler {
       case Some(tablet: item.Tablet) if id == GuiType.Tablet.id => mainItem
       case Some(tablet: item.Tablet) if id == GuiType.TabletInner.id => mainItem
       case Some(terminal: item.Terminal) if id == GuiType.Terminal.id => mainItem
-      case _ => player.inventory.offHandInventory(0)
+      case _ => player.inventory.offHandInventory.get(0)
     }
   }
 }
diff --git a/src/main/scala/li/cil/oc/common/block/DiskDrive.scala b/src/main/scala/li/cil/oc/common/block/DiskDrive.scala
index a222bc5a1..45e56c7e6 100644
--- a/src/main/scala/li/cil/oc/common/block/DiskDrive.scala
+++ b/src/main/scala/li/cil/oc/common/block/DiskDrive.scala
@@ -56,7 +56,7 @@ class DiskDrive extends SimpleBlock with traits.GUI {
           if (hand == EnumHand.MAIN_HAND)
             player.inventory.decrStackSize(player.inventory.currentItem, 1)
           else
-            player.inventory.offHandInventory(0).stackSize -= 1
+            player.inventory.offHandInventory.get(0).shrink(1)
         }
         isDiskInDrive || isHoldingDisk
       case _ => false