diff --git a/asm/6502/decompress_fast_v2.asm b/asm/6502/decompress_fast_v2.asm
index 6b390e3..1e49a75 100644
--- a/asm/6502/decompress_fast_v2.asm
+++ b/asm/6502/decompress_fast_v2.asm
@@ -114,10 +114,9 @@ NO_LITERALS
    BNE GOT_OFFSET_LO                    ; go store low byte of match offset and prepare match
    
 OFFSET_9_BIT                            ; 01Z: 9 bit offset
-   ROL
-   ROL
-   AND #$01
-   EOR #$FF                             ; set offset bits 15-9 to 1
+   ROL                                  ; carry: Z bit; A: xxxxxxx1 (carry known set from BCS OFFSET_9_BIT)
+   ADC #$00                             ; if Z bit is set, add 1 to A (bit 0 of A is now 0), otherwise bit 0 is 1
+   ORA #$FE                             ; set offset bits 15-9 to 1. reversed Z is already in bit 0
    BNE GOT_OFFSET_HI                    ; go store high byte, read low byte of match offset and prepare match
                                         ; (*same as JMP GOT_OFFSET_HI but shorter)