--- a/src/hotspot/share/gc/shared/ptrQueue.hpp	Fri Jan 04 20:58:35 2019 +0100
+++ b/src/hotspot/share/gc/shared/ptrQueue.hpp	Fri Jan 04 15:06:01 2019 -0500
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -29,6 +29,7 @@
 #include "utilities/sizes.hpp"
 
 class Mutex;
+class Monitor;
 
 // There are various techniques that require threads to be able to log
 // addresses.  For example, a generational write barrier might log