diff --git a/libsrc/common/copydata.s b/libsrc/common/copydata.s
index 10f409ca9..b0a9987fd 100644
--- a/libsrc/common/copydata.s
+++ b/libsrc/common/copydata.s
@@ -1,53 +1,49 @@
 ;
-; Ullrich von Bassewitz, 07.12.1998
+; Ullrich von Bassewitz, 1998-12-07, 2004-12-01
 ;
 ; Copy the data segment from the LOAD to the RUN location
 ;
 
 	.export		copydata
 	.import		__DATA_LOAD__, __DATA_RUN__, __DATA_SIZE__
-	.importzp	ptr1, ptr2
+	.importzp	ptr1, ptr2, tmp1
 
 
 copydata:
-	lda    	#<__DATA_LOAD__	; Source pointer
+	lda    	#<__DATA_LOAD__	        ; Source pointer
 	sta	ptr1
 	lda	#>__DATA_LOAD__
 	sta	ptr1+1
 
-	lda	#<__DATA_RUN__	; Target pointer
+	lda	#<__DATA_RUN__	        ; Target pointer
 	sta	ptr2
 	lda	#>__DATA_RUN__
 	sta	ptr2+1
 
-	ldy	#$00
-	ldx	#>__DATA_SIZE__	; Get page count
-	beq	@L2 		; No full pages
+        ldx     #<~__DATA_SIZE__
+        lda     #>~__DATA_SIZE__        ; Use -(__DATASIZE__+1)
+        sta     tmp1
+        ldy     #$00
 
-; Copy full pages
+; Copy loop
 
-@L1:	lda	(ptr1),y
-    	sta	(ptr2),y
-    	iny
-    	bne	@L1
-	inc	ptr1+1
-	inc	ptr2+1		; Bump pointers
-    	dex
-	bne	@L1
+@L1:    inx
+        beq     @L3
 
-; Copy last page (remember: y contains zero)
+@L2:    lda	(ptr1),y
+        sta	(ptr2),y
+        iny
+        bne     @L1
+        inc	ptr1+1
+        inc	ptr2+1	       	        ; Bump pointers
+        bne	@L1		        ; Branch always (hopefully)
 
-@L2:	ldx	#<__DATA_SIZE__	; Get remaining bytes
-    	beq	@L4
+; Bump the high counter byte
 
-@L3:	lda	(ptr1),y
-    	sta	(ptr2),y
-    	iny
-    	dex
-    	bne	@L3
+@L3:    inc     tmp1
+        bne     @L2
 
 ; Done
 
-@L4:	rts
-
+        rts