diff --git a/compiler/res/prog8lib/c64/syslib.p8 b/compiler/res/prog8lib/c64/syslib.p8
index 56cce7440..7461de07e 100644
--- a/compiler/res/prog8lib/c64/syslib.p8
+++ b/compiler/res/prog8lib/c64/syslib.p8
@@ -502,11 +502,9 @@ sys {
         ; --- busy wait till the next vsync has occurred (approximately), without depending on custom irq handling.
         ;     note: a more accurate way to wait for vsync is to set up a vsync irq handler instead.
         %asm {{
--           lda  c64.RASTER
-            beq  -
--           lda  c64.RASTER
-            bne  -
-            bit  c64.SCROLY
+-           bit  c64.SCROLY
+            bpl  -
+-           bit  c64.SCROLY
             bmi  -
             rts
         }}