diff --git a/src/main.lua b/src/main.lua
index 81fb785..d7224eb 100644
--- a/src/main.lua
+++ b/src/main.lua
@@ -243,16 +243,20 @@ local function move(direction)
 end
 local function place(direction)
     local func = turtle.place
+    local cfunc = turtle.compare
     if direction == "down" then
         func = turtle.placeDown
+        cfunc = turtle.compareDown
     end
     if direction == "up" then
         func = turtle.placeUp
+        cfunc = turtle.compareUp
     end
 
     while true do
         local suc = func()
         if not suc then -- next slot
+            if cfunc() and turtle.getItemDetail(turtle.getSelectedSlot())["name"] ~= "minecraft:air" then return end
             local current = turtle.getSelectedSlot()
             if current == 16 then
                 turtle.select(1)