diff --git a/kernel/blockdev.asm b/kernel/blockdev.asm
index ab9f493..a8f8621 100644
--- a/kernel/blockdev.asm
+++ b/kernel/blockdev.asm
@@ -28,7 +28,9 @@
 ;
 ; Unsuccessful writes generally mean that we're out of bounds for writing.
 ;
-; All routines are expected to preserve unused registers.
+; All routines are expected to preserve unused registers except IX which is
+; explicitly protected during GetC/PutC calls. This makes quick "handle+jump"
+; definitions possible.
 
 
 ; *** DEFINES ***
diff --git a/kernel/sdc.asm b/kernel/sdc.asm
index ddced67..f4bdd6c 100644
--- a/kernel/sdc.asm
+++ b/kernel/sdc.asm
@@ -589,7 +589,7 @@ _sdcPlaceBuf:
 	; (SDC_BUFPTR). Only the 9 low bits of HL are important.
 	push	de
 	ld	de, (SDC_BUFPTR)
-	inc	de		; sector LSB
+	inc	de		; sector MSB
 	inc	de		; dirty flag
 	inc	de		; contents
 	ld	a, h		; high byte