--- old/src/hotspot/share/runtime/arguments.cpp	2018-09-17 23:33:12.103737960 -0700
+++ new/src/hotspot/share/runtime/arguments.cpp	2018-09-17 23:33:11.851737968 -0700
@@ -577,6 +577,7 @@
   { "EmitSync",                      JDK_Version::undefined(), JDK_Version::jdk(12), JDK_Version::jdk(13) },
   { "SyncVerbose",                   JDK_Version::undefined(), JDK_Version::jdk(12), JDK_Version::jdk(13) },
   { "SyncFlags",                     JDK_Version::undefined(), JDK_Version::jdk(12), JDK_Version::jdk(13) },
+  { "SyncKnobs",                     JDK_Version::undefined(), JDK_Version::jdk(12), JDK_Version::jdk(13) },
 
 #ifdef TEST_VERIFY_SPECIAL_JVM_FLAGS
   { "dep > obs",                    JDK_Version::jdk(9), JDK_Version::jdk(8), JDK_Version::undefined() },