--- old/src/share/classes/java/lang/ref/ReferenceQueue.java	2013-07-01 10:46:26.234830822 +0200
+++ new/src/share/classes/java/lang/ref/ReferenceQueue.java	2013-07-01 10:46:25.886830829 +0200
@@ -58,6 +58,11 @@
         synchronized (r) {
             if (r.queue == ENQUEUED) return false;
             synchronized (lock) {
+                // Check that since getting the lock this reference hasn't already been
+                // enqueued (and even then removed)
+                if (r.queue != this) {
+                    return false;
+                }
                 r.queue = ENQUEUED;
                 r.next = (head == null) ? r : head;
                 head = r;