diff --git a/wip-hugo/routines/line/line_up_inv.s b/wip-hugo/routines/line/line_up_inv.s
index a99b39b..44719e8 100644
--- a/wip-hugo/routines/line/line_up_inv.s
+++ b/wip-hugo/routines/line/line_up_inv.s
@@ -34,7 +34,7 @@
         STA D + 1
 
         ;; because C flag is wrong value we let dy_2 be 1 to small
-        Sub_16 dy_2, dy_2 +1, #$01,#$00
+        Sub_16 dx_2, dx_2 +1, #$01,#$00
 
 selfmod:
         LDA dx_2