diff --git a/Platform/Apple/virtual/src/core/mem.s b/Platform/Apple/virtual/src/core/mem.s
index 6d3f2333..3c981d68 100644
--- a/Platform/Apple/virtual/src/core/mem.s
+++ b/Platform/Apple/virtual/src/core/mem.s
@@ -1108,7 +1108,7 @@ partFileOpen:	!byte 0
 curMarkPos:	!fill 3
 setMarkPos:	!fill 3
 nSegsQueued:	!byte 0
-;bufferDigest:	!fill 4
+bufferDigest:	!fill 4
 diskActState:	!byte 0
 floppyDrive:	!byte 0
 
@@ -1939,63 +1939,68 @@ diskLoader: !zone
 ; out ok, resulting in a crash. Taking out the digest stuff for now.
 ; !! END NOTE !!
 ;
-; calcBufferDigest: !zone
-; 	lda #>headerBuf
-; 	sta .ld1+2
-; 	sta .ld3+2
-; 	lda #>headerBuf+$A00
-; 	sta .ld2+2
-; 	sta .ld4+2
-; 	ldy #0
-; 	sty tmp
-; 	sty tmp+1
-; 	sty tmp+2
-; 	sty tmp+3
-; 	ldx #6		; sum 6 pages in each area - covers first part of heap collect zone also
-; 	clc
-; .sum	lda tmp
-; 	rol
-; .ld1	adc $1000,y	; high byte self-modified earlier
-; 	sta tmp
+calcBufferDigest: !zone
+	lda #>headerBuf
+	sta .ld1+2
+	sta .ld3+2
+	lda #>headerBuf+$A00
+	sta .ld2+2
+	sta .ld4+2
+	ldy #0
+	sty tmp
+	sty tmp+1
+	sty tmp+2
+	sty tmp+3
+	ldx #6		; sum 6 pages in each area - covers first part of heap collect zone also
+	clc
+.nxtpg	ldy #0
+.sum	lda tmp
+	rol
+.ld1	adc $1000,y	; high byte self-modified earlier
+	eor tmp+1
+	sta tmp
 
-; 	lda tmp+1
-; 	rol
-; .ld2	adc $1000,y	; high byte self-modified earlier
-; 	sta tmp+1
+	lda tmp+1
+	rol
+.ld2	adc $1000,y	; high byte self-modified earlier
+	eor tmp+2
+	sta tmp+1
 
-; 	lda tmp+2
-; 	rol
-; .ld3	adc $1080,y	; high byte self-modified earlier
-; 	sta tmp+2
+	lda tmp+2
+	rol
+.ld3	adc $1080,y	; high byte self-modified earlier
+	eor tmp+3
+	sta tmp+2
 
-; 	lda tmp+3
-; 	rol
-; .ld4	adc $1080,y	; high byte self-modified earlier
-; 	sta tmp+3
+	lda tmp+3
+	rol
+.ld4	adc $1080,y	; high byte self-modified earlier
+	eor tmp
+	sta tmp+3
 
-; 	iny
-; 	iny
-; 	bpl .sum	; every even offset 0..126
+	iny
+	iny
+	bpl .sum	; every even offset 0..126
 
-; 	inc .ld1+2	; go to next page
-; 	inc .ld2+2
-; 	inc .ld3+2
-; 	inc .ld4+2
-; 	dex
-; 	bne .ld1
+	inc .ld1+2	; go to next page
+	inc .ld2+2
+	inc .ld3+2
+	inc .ld4+2
+	dex
+	bne .nxtpg
 
-; 	; Now compare with the old digest, and replace the old digest.
-; .cmp	ldy #0
-; 	ldx #3
-; -	lda tmp,x
-; 	cmp bufferDigest,x
-; 	beq +
-; 	iny
-; +	sta bufferDigest,x
-; 	dex
-; 	bpl -
-; 	cpy #0	; Y=0 if new digest equals old digest
-; 	rts
+	; Now compare with the old digest, and replace the old digest.
+.cmp	ldy #0
+	ldx #3
+-	lda tmp,x
+	cmp bufferDigest,x
+	beq +
+	iny
++	sta bufferDigest,x
+	dex
+	bpl -
+	cpy #0	; Y=0 if new digest equals old digest
+	rts
 
 ;------------------------------------------------------------------------------
 openPartition: !zone
@@ -2090,8 +2095,8 @@ disk_startLoad: !zone
 	bne .new		; if different, close the old one
 	lda partFileOpen
 	beq .done		; if nothing already open, we're okay with that.
-	;jsr calcBufferDigest	; same partition - check that buffers are still intact
-	;beq .done		; if correct partition file already open, we're done.
+	jsr calcBufferDigest	; same partition - check that buffers are still intact
+	beq .done		; if correct partition file already open, we're done.
 .new	lda nSegsQueued		; make sure nothing queued before switching
 	bne sequenceError
 	jsr closePartFile
@@ -2274,7 +2279,7 @@ disk_finishLoad: !zone
 .scan:	lda (pTmp),y		; get resource type byte
 	bne .notdone		; zero = end of header
 	; At the end, record new buffer digest, and perform all fixups
-	;jsr calcBufferDigest
+	jsr calcBufferDigest
 	lda .nFixups		; any fixups encountered?
 	beq .done
 	jsr doAllFixups		; found fixups - execute and free them