diff --git a/build_circle.lua b/build_circle.lua
index bfceba1..b304e98 100644
--- a/build_circle.lua
+++ b/build_circle.lua
@@ -49,6 +49,7 @@ file:close()
 local inverted = false
 
 robot.select(1)
+local inventorySize = robot.inventorySize()
 
 -- build:
 nav.forward(radius)
@@ -65,7 +66,18 @@ for _, ring in ipairs(rings) do
                 for _ = 1, n do
                     robot.placeDown()
                     if robot.count() == 0 then
-                        robot.select(robot.select() + 1) -- select the next item slot
+                        local current_slot = robot.select()
+                        if current_slot == inventorySize then
+                            print('Waiting for more materials')
+                            local _ = io.read()
+                            robot.select(1)
+                        else
+                            robot.select(current_slot + 1) -- select the next item slot
+                            if robot.count() == 0 then
+                                print('Waiting for more materials')
+                                local _ = io.read()
+                            end
+                        end
                     end
                     nav.forward()
                 end
diff --git a/rings b/rings
index 4637312..bf972db 100644
--- a/rings
+++ b/rings
@@ -4,3 +4,4 @@
 822221111X11122227
 83322211X1222337
 83322211X11222337
+833222111X11222337