diff --git a/source/kernel/bank4/partit.mac b/source/kernel/bank4/partit.mac
index 46d3ea8a..60c189e3 100644
--- a/source/kernel/bank4/partit.mac
+++ b/source/kernel/bank4/partit.mac
@@ -3138,7 +3138,7 @@ MAP_SPECIFIC:
 
 MAP_DRV_UNK:
 	;Unknown change status: assume unchanged media.
-	;If it has changed, the boot checksum checksum
+	;If it has changed, the boot checksum
 	;mechanism will do the work of unassigning
 	;all other drives mapped to this device
 	;if necessary.
@@ -3148,6 +3148,7 @@ MAP_DRV_UNK:
 MAP_DRV_CH:
 	push	hl
 	push	iy
+	push	bc
 	ld	e,(hl)
 	inc	hl
 	ld	d,(hl)
@@ -3157,6 +3158,7 @@ MAP_DRV_CH:
 	ld	d,(iy+2)
 	ld	e,(iy+3)
 	call	UNMAPALL
+	pop bc
 	pop	iy
 	pop	hl
 
diff --git a/source/kernel/drivers/MegaFlashRomSD/mfrsd.asm b/source/kernel/drivers/MegaFlashRomSD/mfrsd.asm
index 63825574..5c13e030 100644
--- a/source/kernel/drivers/MegaFlashRomSD/mfrsd.asm
+++ b/source/kernel/drivers/MegaFlashRomSD/mfrsd.asm
@@ -666,7 +666,7 @@ DEV_RW:
 
 	;ld	hl,(#f9f0)
 	;inc	hl
-	;ld	(#f9f0),hl	; Cuenta lecturas
+	;ld	(#f9f0),hl	; Count reads
 		
 	call	SD_OFF
 	ei
@@ -677,6 +677,9 @@ DEV_RW:
 	ret
 	
 .ok:	
+	;A successful device access must reset the "device changed" flag
+	res	BIT_SD_CHG,(ix+STATUS)
+
 	xor	a		; Ok
 	ret