diff -Naur --strip-trailing-cr jmx.old/AbstractDynamicMBean.java jmx/AbstractDynamicMBean.java
--- jmx.old/AbstractDynamicMBean.java	2005-12-05 03:00:54.000000000 +0100
+++ jmx/AbstractDynamicMBean.java	2006-08-14 14:02:41.530518400 +0200
@@ -17,6 +17,7 @@
 package org.apache.log4j.jmx;
 
 //import java.lang.reflect.Constructor;
+import java.util.Collection;
 import java.util.Iterator;
 import javax.management.DynamicMBean;
 import javax.management.AttributeList;
@@ -25,6 +26,10 @@
 import javax.management.MBeanRegistration;
 import javax.management.MBeanServer;
 import javax.management.ObjectName;
+import javax.management.InstanceAlreadyExistsException;
+import javax.management.InstanceNotFoundException;
+import javax.management.MBeanRegistrationException;
+import javax.management.NotCompliantMBeanException;
 
 import org.apache.log4j.Logger;
 
@@ -33,6 +38,9 @@
 
   String dClassName;
   MBeanServer server;
+  
+  /** List of MBean names which are registered internally. */
+  private Collection mbeanList = new java.util.LinkedList();
 
   /**
    * Enables the to get the values of several attributes of the Dynamic MBean.
@@ -112,10 +120,37 @@
   }
 
 
+  /**
+   * Registers MBean instance in the attached server. Must <em>NOT</em>
+   * be called before registration if this instance.
+   */
+  protected
+  void registerMBean(Object mbean, ObjectName objectName)
+  throws InstanceAlreadyExistsException, MBeanRegistrationException,
+					NotCompliantMBeanException {
+    server.registerMBean(mbean, objectName);
+    mbeanList.add(objectName);
+  }
 
+  /**
+   * Performs cleanup for deregistering this MBean. Default implementation
+   * unregisters MBean instances which are registered using 
+   * {@link #registerMBean(Object mbean, ObjectName objectName)}.
+   */
   public
   void preDeregister() {
     getLogger().debug("preDeregister called.");
+    Iterator iterator = mbeanList.iterator();
+    while (iterator.hasNext()) {
+      ObjectName name = (ObjectName) iterator.next();
+      try {
+        server.unregisterMBean(name);
+      } catch (InstanceNotFoundException e) {
+	getLogger().warn("Missing MBean " + name.getCanonicalName());
+      } catch (MBeanRegistrationException e) {
+	getLogger().warn("Failed unregistering " + name.getCanonicalName());
+      }
+    }
   }
 
   public
diff -Naur --strip-trailing-cr jmx.old/AppenderDynamicMBean.java jmx/AppenderDynamicMBean.java
--- jmx.old/AppenderDynamicMBean.java	2006-08-14 13:42:53.782620000 +0200
+++ jmx/AppenderDynamicMBean.java	2006-08-14 14:00:04.344496000 +0200
@@ -192,7 +192,7 @@
     try {
       LayoutDynamicMBean appenderMBean = new LayoutDynamicMBean(layout);
       objectName = new ObjectName("log4j:appender="+name);
-      server.registerMBean(appenderMBean, objectName);
+      registerMBean(appenderMBean, objectName);
 
       dAttributes.add(new MBeanAttributeInfo("appender="+name,
 					     "javax.management.ObjectName",
diff -Naur --strip-trailing-cr jmx.old/HierarchyDynamicMBean.java jmx/HierarchyDynamicMBean.java
--- jmx.old/HierarchyDynamicMBean.java	2006-08-14 13:42:49.967134000 +0200
+++ jmx/HierarchyDynamicMBean.java	2006-08-14 14:12:29.305697600 +0200
@@ -117,7 +117,7 @@
     try {
       LoggerDynamicMBean loggerMBean = new LoggerDynamicMBean(logger);
       objectName = new ObjectName("log4j", "logger", name);
-      server.registerMBean(loggerMBean, objectName);
+      registerMBean(loggerMBean, objectName);
 
       NotificationFilterSupport nfs = new NotificationFilterSupport();
       nfs.enableType(ADD_APPENDER+logger.getName());
diff -Naur --strip-trailing-cr jmx.old/LoggerDynamicMBean.java jmx/LoggerDynamicMBean.java
--- jmx.old/LoggerDynamicMBean.java	2005-12-05 03:00:52.000000000 +0100
+++ jmx/LoggerDynamicMBean.java	2006-08-14 13:59:59.807972800 +0200
@@ -257,7 +257,7 @@
     try {
       AppenderDynamicMBean appenderMBean = new AppenderDynamicMBean(appender);
       objectName = new ObjectName("log4j", "appender", name);
-      server.registerMBean(appenderMBean, objectName);
+      registerMBean(appenderMBean, objectName);
 
       dAttributes.add(new MBeanAttributeInfo("appender="+name,
 					     "javax.management.ObjectName",