diff --git a/messages.asm b/messages.asm
index 0ee0a69..3dbb85d 100644
--- a/messages.asm
+++ b/messages.asm
@@ -167,7 +167,8 @@ beep:
 	;; see #NOTE_LOOP
 	;; the duration counter gets decremented BEFORE
 	;; it gets compared to zero
-	sub al, 'b' 	; normalise (a=1, b=2, c=...)
+	;; ('a' is 0x61)
+	sub al, 0x60 	; normalise (a=1, b=2, c=...)
 
 	;; interrupt 0x16, ah=0 returns the read scancode in ah
 	;; so ah must be reset
@@ -214,7 +215,7 @@ beep:
 
 	;; #NOTE_LOOP
 	;; the duration gets decremented before being checked
-	;; hence why it was normalised to 'b' and not 'a'
+	;; hence why it was normalised to '`' and not 'a'
 	dec     ax	; decrement duration counter
 	jne     .pause1	; keep doing that until it is 0