diff --git a/libsrc/atmos/write.s b/libsrc/atmos/write.s
index d5a693ada..b7129dd1a 100644
--- a/libsrc/atmos/write.s
+++ b/libsrc/atmos/write.s
@@ -15,7 +15,7 @@
 .proc   _write
 
 	sta	ptr3
-	sta	ptr3+1	     	; save count as result
+       	stx     ptr3+1	     	; save count as result
 
         eor     #$FF
         sta     ptr2