diff --git a/cpu/6502/net/cs8900a.S b/cpu/6502/net/cs8900a.S
index e0a0837af..226d8606e 100644
--- a/cpu/6502/net/cs8900a.S
+++ b/cpu/6502/net/cs8900a.S
@@ -206,9 +206,8 @@ fixup13:lda rxtxreg
 	jsr adjustcnt
 
 	; Is bufsize < cnt ?
-	sec
 	lda bufsize
-	sbc cnt
+	cmp cnt
 	lda bufsize+1
 	sbc cnt+1
 	bcs :+
@@ -334,6 +333,7 @@ adjustcnt:
 
 adjustptr:
 	lda cnt
+	ldx cnt+1
 	eor #$FF		; Two's complement part 1
 	tay
 	iny			; Two's complement part 2
@@ -345,7 +345,6 @@ adjustptr:
 	lda bufaddr+1
 	sbc #$00
 	sta ptr+1
-	ldx cnt+1
 	rts
 
 ;---------------------------------------------------------------------
diff --git a/cpu/6502/net/lan91c96.S b/cpu/6502/net/lan91c96.S
index d943ca1b1..d034b9788 100644
--- a/cpu/6502/net/lan91c96.S
+++ b/cpu/6502/net/lan91c96.S
@@ -248,9 +248,8 @@ fixup20:lda ethdata
 	sta len+1
 
 	; Is bufsize < len ?
-	sec
 	lda bufsize
-	sbc len
+	cmp len
 	lda bufsize+1
 	sbc len+1
 	bcs :+
@@ -389,6 +388,7 @@ exit:
 
 adjustptr:
 	lda len
+	ldx len+1
 	eor #$FF		; Two's complement part 1
 	tay
 	iny			; Two's complement part 2
@@ -400,7 +400,6 @@ adjustptr:
 	lda bufaddr+1
 	sbc #$00
 	sta ptr+1
-	ldx len+1
 	rts
 
 ;---------------------------------------------------------------------