diff -r 29b0d0b61615 -r a6deb69743d4 src/hotspot/share/gc/z/zForwarding.inline.hpp
--- a/src/hotspot/share/gc/z/zForwarding.inline.hpp	Mon Nov 25 12:31:39 2019 +0100
+++ b/src/hotspot/share/gc/z/zForwarding.inline.hpp	Mon Nov 25 12:32:07 2019 +0100
@@ -76,7 +76,7 @@
 
 inline bool ZForwarding::dec_refcount() {
   assert(_refcount > 0, "Invalid state");
-  return Atomic::sub(1u, &_refcount) == 0u;
+  return Atomic::sub(&_refcount, 1u) == 0u;
 }
 
 inline bool ZForwarding::retain_page() {