--- old/src/share/classes/java/util/prefs/AbstractPreferences.java	Tue May  1 11:51:14 2012
+++ new/src/share/classes/java/util/prefs/AbstractPreferences.java	Tue May  1 11:51:12 2012
@@ -307,6 +307,7 @@
      *         removed with the {@link #removeNode()} method.
      */
     public void remove(String key) {
+        Objects.requireNonNull(key, "Specified key cannot be null");
         synchronized(lock) {
             if (removed)
                 throw new IllegalStateException("Node has been removed.");