diff --git a/technic/machines/mv/alloy_furnace.lua b/technic/machines/mv/alloy_furnace.lua
index b7a837f..1809262 100644
--- a/technic/machines/mv/alloy_furnace.lua
+++ b/technic/machines/mv/alloy_furnace.lua
@@ -262,8 +262,7 @@ minetest.register_abm(
 
 		   -- The machine shuts down if we have nothing to smelt and no tube is connected
 		   -- or if we have nothing to send with a tube connected.
-		   if    (not output_tube_connected and inv:is_empty("src"))
-		      or (    output_tube_connected and inv:is_empty("dst")) then
+		   if inv:is_empty("src") and (not output_tube_connected or inv:is_empty("dst")) then
 		      next_state = 1
 		   end
 		   ----------------------
diff --git a/technic/machines/mv/electric_furnace.lua b/technic/machines/mv/electric_furnace.lua
index a125d4b..c6a1651 100644
--- a/technic/machines/mv/electric_furnace.lua
+++ b/technic/machines/mv/electric_furnace.lua
@@ -262,8 +262,7 @@ minetest.register_abm(
 		   
 		   -- The machine shuts down if we have nothing to smelt and no tube is connected
 		   -- or if we have nothing to send with a tube connected.
-		   if    (not output_tube_connected and inv:is_empty("src"))
-		   or (    output_tube_connected and inv:is_empty("dst")) then
+		   if inv:is_empty("src") and (not output_tube_connected or inv:is_empty("dst")) then
 		   next_state = 1
 		end
 		----------------------
diff --git a/technic/machines/mv/grinder.lua b/technic/machines/mv/grinder.lua
index e993794..84710c9 100644
--- a/technic/machines/mv/grinder.lua
+++ b/technic/machines/mv/grinder.lua
@@ -239,8 +239,7 @@ minetest.register_abm(
 
 			-- The machine shuts down if we have nothing to grind and no tube is connected
 			-- or if we have nothing to send with a tube connected.
-			if    (not output_tube_connected and inv:is_empty("src"))
-			or (    output_tube_connected and inv:is_empty("dst")) then
+			if inv:is_empty("src") and (not output_tube_connected or inv:is_empty("dst")) then
 				next_state = 1
 			end