--- old/src/hotspot/cpu/aarch64/globals_aarch64.hpp	2019-10-17 17:31:16.000000000 -0400
+++ new/src/hotspot/cpu/aarch64/globals_aarch64.hpp	2019-10-17 17:31:15.000000000 -0400
@@ -75,6 +75,9 @@
 define_pd_global(intx, InitArrayShortSize, BytesPerLong);
 
 define_pd_global(bool, ThreadLocalHandshakes, true);
+// ObjectMonitor ref_count not implemented in C2 fast_lock() or
+// fast_unlock() so use a handshake for safety.
+define_pd_global(bool, HandshakeAfterDeflateIdleMonitors, true);
 
 #if defined(COMPILER1) || defined(COMPILER2)
 define_pd_global(intx, InlineSmallCode,          1000);