diff --git a/mystical-upgrader.lua b/mystical-upgrader.lua
index 93a08ba..c7f2194 100644
--- a/mystical-upgrader.lua
+++ b/mystical-upgrader.lua
@@ -59,31 +59,29 @@ local refuel = function()
   end
 end
 
-local goToTheLeft = function()
-  turtle.turnLeft()
-  local ok, reason = turtle.forward()
-
-  if not ok then
-    error('cannot forward because ' .. tostring(reason), 0)
-  end
-
-  turtle.turnRight()
-end
-
-local goToTheRight = function()
-  turtle.turnRight()
-  local ok, reason = turtle.forward()
-
-  if not ok then
-    error('cannot forward because ' .. tostring(reason), 0)
-  end
-
-  turtle.turnLeft()
-end
-
 local MOVES = {
-  left = goToTheLeft,
-  right = goToTheRight,
+  left =  function(strictMode)
+    turtle.turnLeft()
+    local ok, reason = turtle.forward()
+
+    if strictMode and not ok then
+      error('cannot forward because ' .. tostring(reason), 0)
+    end
+
+    turtle.turnRight()
+    return ok, reason
+  end,
+  right = function(strictMode)
+    turtle.turnRight()
+    local ok, reason = turtle.forward()
+
+    if strictMode and not ok then
+      error('cannot forward because ' .. tostring(reason), 0)
+    end
+
+    turtle.turnLeft()
+    return ok, reason
+  end,
 }
 
 local getTierFromLevel = function(level)
@@ -262,7 +260,9 @@ local main = function()
     upgradeProcedure()
 
     if i ~= NB_ROWS then
-      MOVES[DIRECTION]()
+      MOVES[DIRECTION](true)
+    else
+      MOVES[DIRECTION](false) -- do not throw if cannot move forward
     end
   end