diff --git a/asm_routines/dos33_routines.s b/asm_routines/dos33_routines.s
index db05df04..d96201c0 100644
--- a/asm_routines/dos33_routines.s
+++ b/asm_routines/dos33_routines.s
@@ -73,7 +73,7 @@ filename_pad_spaces:
 	lda	#$A0			; filename needs ' ' padded
 	sta	(OUTL),y
 	iny
-	cpy	#31			; fill 30 bytes
+	cpy	#30			; fill 30 bytes
 	bne	filename_pad_spaces