diff --git a/libsrc/telestrat/read.s b/libsrc/telestrat/read.s
index f31909f45..b89f246cc 100644
--- a/libsrc/telestrat/read.s
+++ b/libsrc/telestrat/read.s
@@ -30,13 +30,14 @@
         ldy     ptr1+1
         BRK_TELEMON     XFREAD
         ;  compute nb of bytes read
-        lda     PTR_READ_DEST+1
         sec
-        sbc     ptr2+1
-        tax
-        lda     PTR_READ_DEST
-        sec
-        sbc     ptr2
-        ; here A and X contains number of bytes read
+	lda     PTR_READ_DEST
+	sbc     ptr2
+	sta     tmp1
+	lda     PTR_READ_DEST+1
+	sbc     ptr2+1
+	tax
+        lda     tmp1
+
         rts
 .endproc
diff --git a/libsrc/telestrat/write.s b/libsrc/telestrat/write.s
index 2ce2657ac..06524f749 100644
--- a/libsrc/telestrat/write.s
+++ b/libsrc/telestrat/write.s
@@ -42,16 +42,16 @@ next:
         ldy     ptr3+1
         ldx     tmp1            ; send fd in X
         BRK_TELEMON  XFWRITE
+
         ;  compute nb of bytes written
-
-
-        lda     PTR_READ_DEST+1
         sec
-        sbc     ptr1+1
-        tax
-        lda     PTR_READ_DEST
-        sec
-        sbc     ptr1
+	lda     PTR_READ_DEST
+	sbc     ptr1
+	sta     tmp1
+	lda     PTR_READ_DEST+1
+	sbc     ptr1+1
+	tax
+        lda     tmp1
         rts