--- old/src/hotspot/share/runtime/arguments.cpp	2020-08-14 16:28:45.285505008 +0200
+++ new/src/hotspot/share/runtime/arguments.cpp	2020-08-14 16:28:45.065501086 +0200
@@ -552,6 +552,7 @@
 #endif
   { "PrintVMQWaitTime",              JDK_Version::jdk(15), JDK_Version::jdk(16), JDK_Version::jdk(17) },
   { "UseNewFieldLayout",             JDK_Version::jdk(15), JDK_Version::jdk(16), JDK_Version::jdk(17) },
+  { "UseSemaphoreGCThreadsSynchronization", JDK_Version::undefined(), JDK_Version::jdk(16), JDK_Version::jdk(17) },
 
 #ifdef TEST_VERIFY_SPECIAL_JVM_FLAGS
   // These entries will generate build errors.  Their purpose is to test the macros.