diff --git a/storage/itemstack.lua b/storage/itemstack.lua
index dc0367a..3401d36 100644
--- a/storage/itemstack.lua
+++ b/storage/itemstack.lua
@@ -1,6 +1,7 @@
 local Inventory = require("storage.inventory")
 local Sentinel = require("storage.sentinel")
-local Logger = require("logging").getGlobalLogger()
+local Logging = require("logging")
+local Logger = Logging.getGlobalLogger()
 
 local ItemStack = Sentinel:tag({}, Sentinel.ITEMSTACK)
 ItemStack.__index = ItemStack
@@ -157,9 +158,6 @@ function ItemStack:hasChanged(listObj, thorough)
 end
 
 function ItemStack:_modify(countDelta, stack)
-  if countDelta == nil then
-    Logger:error("countDelta is nil!", stack)
-  end
   local newCount = self:getCount() + countDelta
   if newCount < 0 then
     error("ERROR: New stack count is negative: "..newCount)
@@ -207,6 +205,15 @@ function ItemStack:transferTo(target, count)
     return false, xfer
   end
 
+  if xfer == nil then
+    Logger:error(
+      "Error transferring item", self:getInventory().pushItems, Logger.plain("\n"),
+      peripheral.getName(target:getInventory()), Logger.plain("\n"),
+      self:getSlot(), cap, Logger.plain("\n"),
+      target
+    )
+  end
+
   target:_modify(xfer, self)
   self:_modify(-xfer, self)