Index: /trunk/ccl/level-0/X86/x86-misc.lisp
===================================================================
--- /trunk/ccl/level-0/X86/x86-misc.lisp	(revision 5402)
+++ /trunk/ccl/level-0/X86/x86-misc.lisp	(revision 5403)
@@ -176,7 +176,9 @@
 
 (defx86lapfunction %heap-bytes-allocated ()
+  (movq (@ (% :rcontext) x8664::tcr.save-allocptr) (% temp1))
   (movq (@ (% :rcontext) x8664::tcr.last-allocptr) (% temp0))
-  (movq (@ (% :rcontext) x8664::tcr.save-allocptr) (% temp1))
+  (cmpq ($ -16) (% temp1))
   (movq (@ (% :rcontext) x8664::tcr.total-bytes-allocated) (% imm0))
+  (jz @go)
   (movq (% temp0) (% temp2))
   (subq (% temp1) (% temp0))