--- a/hotspot/src/share/vm/gc_implementation/shared/vmGCOperations.cpp	Thu Feb 03 16:06:01 2011 -0500
+++ b/hotspot/src/share/vm/gc_implementation/shared/vmGCOperations.cpp	Thu Feb 03 20:49:09 2011 -0800
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2011, 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
@@ -87,6 +87,8 @@
 
 bool VM_GC_Operation::doit_prologue() {
   assert(Thread::current()->is_Java_thread(), "just checking");
+  assert(((_gc_cause != GCCause::_no_gc) &&
+          (_gc_cause != GCCause::_no_cause_specified)), "Illegal GCCause");
 
   acquire_pending_list_lock();
   // If the GC count has changed someone beat us to the collection