--- old/src/cpu/zero/vm/stack_zero.inline.hpp	2016-01-04 13:47:07.777866645 -0500
+++ new/src/cpu/zero/vm/stack_zero.inline.hpp	2016-01-04 13:47:07.693866643 -0500
@@ -49,11 +49,10 @@
 // value can be negative.
 inline int ZeroStack::abi_stack_available(Thread *thread) const {
   guarantee(Thread::current() == thread, "should run in the same thread");
-  assert(thread->stack_size() -
-         (thread->stack_base() - (address) &stack_used +
-          JavaThread::stack_guard_zone_size() + JavaThread::stack_shadow_zone_size()) ==
-         (address)&stack_used - thread->stack_overflow_limit(), "sanity");
-  return (address)&stack_used - stack_overflow_limit();
+  int stack_used = thread->stack_base() - (address) &stack_used
+    + (JavaThread::stack_guard_zone_size() + JavaThread::stack_shadow_zone_size());
+  int stack_free = thread->stack_size() - stack_used;
+  return stack_free;
 }
 
 #endif // CPU_ZERO_VM_STACK_ZERO_INLINE_HPP