--- old/src/share/vm/gc/cms/concurrentMarkSweepGeneration.cpp	Wed Jun 10 14:04:19 2015
+++ new/src/share/vm/gc/cms/concurrentMarkSweepGeneration.cpp	Wed Jun 10 14:04:18 2015
@@ -2671,6 +2671,10 @@
 // below.
 void CMSCollector::update_should_unload_classes() {
   _should_unload_classes = false;
+  if (!ClassUnloading) {
+    return;
+  }
+
   // Condition 1 above
   if (_full_gc_requested && ExplicitGCInvokesConcurrentAndUnloadsClasses) {
     _should_unload_classes = true;