diff -r 308762b2bf14 -r 05f89f00a864 src/share/vm/memory/referenceProcessor.cpp
--- a/src/share/vm/memory/referenceProcessor.cpp	Fri Aug 14 13:44:15 2009 -0700
+++ b/src/share/vm/memory/referenceProcessor.cpp	Mon Aug 24 10:36:31 2009 -0700
@@ -1231,6 +1231,11 @@
 
   NOT_PRODUCT(verify_ok_to_handle_reflists());
 
+#ifdef ASSERT
+  bool must_remember_klasses = ClassUnloading && !UseConcMarkSweepGC ||
+                               CMSClassUnloadingEnabled && UseConcMarkSweepGC;
+  RememberKlassesChecker mx(must_remember_klasses);
+#endif
   // Soft references
   {
     TraceTime tt("Preclean SoftReferences", PrintGCDetails && PrintReferenceGC,