diff --git a/coal-crafter.lua b/coal-crafter.lua
index 592328e..fe76098 100644
--- a/coal-crafter.lua
+++ b/coal-crafter.lua
@@ -25,7 +25,7 @@ local function dropAll(side, dropFn)
       turtleUtils.waitForInventory(side, IDLE_TIME)
 
       local errorPrinted = false
-      while not turtleUtils.dropSlot(i, dropFn) do
+      while turtle.getItemCount(i) > 0 and not turtleUtils.dropSlot(i, dropFn) do
         if not errorPrinted then
           print('> please empty the turtle inventory')
           errorPrinted = true
@@ -140,6 +140,10 @@ local function main()
   print('> drop all')
   dropAll(STORAGE_INVENTORY_SIDE, dropInStorageFn)
 
+  if not turtleUtils.isInventoryEmpty() then
+    error('Error: inventory is not empty', 0)
+  end
+
   turtle.select(CRAFTING_SLOT)
   print('> coal-crafter process started')