--- old/src/hotspot/share/runtime/objectMonitor.inline.hpp	2017-10-12 12:06:43.040281894 -0400
+++ new/src/hotspot/share/runtime/objectMonitor.inline.hpp	2017-10-12 12:06:42.619246974 -0400
@@ -37,6 +37,7 @@
 }
 
 inline markOopDesc* volatile* ObjectMonitor::header_addr() {
+  assert((intptr_t)this == (intptr_t)&_header, "sync code expects this");
   return &_header;
 }