diff --git a/src/main/scala/li/cil/oc/server/component/UpgradeInventoryController.scala b/src/main/scala/li/cil/oc/server/component/UpgradeInventoryController.scala
index 5e97814d9..516796292 100644
--- a/src/main/scala/li/cil/oc/server/component/UpgradeInventoryController.scala
+++ b/src/main/scala/li/cil/oc/server/component/UpgradeInventoryController.scala
@@ -76,6 +76,14 @@ object UpgradeInventoryController {
       else result(false)
     }
 
+    // TODO Remove in 1.5
+    @Callback(doc = """function(side:number):number -- Get the number of slots in the inventory on the specified side of the robot.""")
+    override def getInventorySize(context: Context, args: Arguments): Array[AnyRef] = {
+      if (args.optInteger(0, -1) == ForgeDirection.NORTH.ordinal) // sides.back
+        getInventorySize(context, new ArgumentsImpl(args.toArray.drop(1))) // drop side, just pass slot
+      else super.getInventorySize(context, args)
+    }
+
     // TODO Remove in 1.5
     @Callback(doc = """function(side:number, slot:number):table -- Get a description of the stack in the the inventory on the specified side of the robot.""")
     override def getStackInSlot(context: Context, args: Arguments) = {