diff --git a/src/java/com/threerings/presents/dobj/AttributeChangeListener.java b/src/java/com/threerings/presents/dobj/AttributeChangeListener.java
index c4cb3be09..101c551e1 100644
--- a/src/java/com/threerings/presents/dobj/AttributeChangeListener.java
+++ b/src/java/com/threerings/presents/dobj/AttributeChangeListener.java
@@ -1,5 +1,5 @@
 //
-// $Id: AttributeChangeListener.java,v 1.1 2001/10/12 00:03:03 mdb Exp $
+// $Id: AttributeChangeListener.java,v 1.2 2002/02/03 04:38:05 mdb Exp $
 
 package com.threerings.presents.dobj;
 
@@ -9,7 +9,7 @@ package com.threerings.presents.dobj;
  *
  * @see DObject#addListener
  */
-public interface AttributeChangeListener
+public interface AttributeChangeListener extends ChangeListener
 {
     /**
      * Called when an attribute changed event has been dispatched on an
diff --git a/src/java/com/threerings/presents/dobj/ChangeListener.java b/src/java/com/threerings/presents/dobj/ChangeListener.java
new file mode 100644
index 000000000..5fc648b2b
--- /dev/null
+++ b/src/java/com/threerings/presents/dobj/ChangeListener.java
@@ -0,0 +1,16 @@
+//
+// $Id: ChangeListener.java,v 1.1 2002/02/03 04:38:05 mdb Exp $
+
+package com.threerings.presents.dobj;
+
+/**
+ * The various listener interfaces (e.g. {@link EventListener}, {@link
+ * AttributeChangeListener}, etc.) all extend this base interface so that
+ * the distributed object can check to make sure when an object is adding
+ * itself as a listener of some sort that it actually implements at least
+ * one of the listener interfaces. Thus, all listener interfaces must
+ * extend this one.
+ */
+public interface ChangeListener
+{
+}
diff --git a/src/java/com/threerings/presents/dobj/DObject.java b/src/java/com/threerings/presents/dobj/DObject.java
index 7cde55636..45a1fb43e 100644
--- a/src/java/com/threerings/presents/dobj/DObject.java
+++ b/src/java/com/threerings/presents/dobj/DObject.java
@@ -1,5 +1,5 @@
 //
-// $Id: DObject.java,v 1.32 2002/02/02 09:42:36 mdb Exp $
+// $Id: DObject.java,v 1.33 2002/02/03 04:38:05 mdb Exp $
 
 package com.threerings.presents.dobj;
 
@@ -157,7 +157,7 @@ public class DObject
      * @see SetListener
      * @see OidListListener
      */
-    public void addListener (Object listener)
+    public void addListener (ChangeListener listener)
     {
         // only add the listener if they're not already there
         Object[] els = ListUtil.testAndAdd(_listeners, listener);
@@ -172,7 +172,7 @@ public class DObject
      *
      * @param listener the listener to be removed.
      */
-    public void removeListener (Object listener)
+    public void removeListener (ChangeListener listener)
     {
         ListUtil.clear(_listeners, listener);
     }
diff --git a/src/java/com/threerings/presents/dobj/EventListener.java b/src/java/com/threerings/presents/dobj/EventListener.java
index 82339d801..cb7c71a65 100644
--- a/src/java/com/threerings/presents/dobj/EventListener.java
+++ b/src/java/com/threerings/presents/dobj/EventListener.java
@@ -1,5 +1,5 @@
 //
-// $Id: EventListener.java,v 1.1 2001/10/12 00:03:03 mdb Exp $
+// $Id: EventListener.java,v 1.2 2002/02/03 04:38:05 mdb Exp $
 
 package com.threerings.presents.dobj;
 
@@ -9,7 +9,7 @@ package com.threerings.presents.dobj;
  *
  * @see DObject#addListener
  */
-public interface EventListener
+public interface EventListener extends ChangeListener
 {
     /**
      * Called when any event has been dispatched on an object. The event
diff --git a/src/java/com/threerings/presents/dobj/MessageListener.java b/src/java/com/threerings/presents/dobj/MessageListener.java
index 2a610e28b..ad3070650 100644
--- a/src/java/com/threerings/presents/dobj/MessageListener.java
+++ b/src/java/com/threerings/presents/dobj/MessageListener.java
@@ -1,5 +1,5 @@
 //
-// $Id: MessageListener.java,v 1.1 2001/10/12 00:03:03 mdb Exp $
+// $Id: MessageListener.java,v 1.2 2002/02/03 04:38:05 mdb Exp $
 
 package com.threerings.presents.dobj;
 
@@ -9,7 +9,7 @@ package com.threerings.presents.dobj;
  *
  * @see DObject#addListener
  */
-public interface MessageListener
+public interface MessageListener extends ChangeListener
 {
     /**
      * Called when an message event has been dispatched on an object.
diff --git a/src/java/com/threerings/presents/dobj/ObjectDeathListener.java b/src/java/com/threerings/presents/dobj/ObjectDeathListener.java
index d285d70ff..c94016d06 100644
--- a/src/java/com/threerings/presents/dobj/ObjectDeathListener.java
+++ b/src/java/com/threerings/presents/dobj/ObjectDeathListener.java
@@ -1,5 +1,5 @@
 //
-// $Id: ObjectDeathListener.java,v 1.1 2001/10/23 23:56:12 mdb Exp $
+// $Id: ObjectDeathListener.java,v 1.2 2002/02/03 04:38:05 mdb Exp $
 
 package com.threerings.presents.dobj;
 
@@ -9,7 +9,7 @@ package com.threerings.presents.dobj;
  *
  * @see DObject#addListener
  */
-public interface ObjectDeathListener
+public interface ObjectDeathListener extends ChangeListener
 {
     /**
      * Called when this object has been destroyed. This will be called
diff --git a/src/java/com/threerings/presents/dobj/OidListListener.java b/src/java/com/threerings/presents/dobj/OidListListener.java
index de5394f85..716d785fe 100644
--- a/src/java/com/threerings/presents/dobj/OidListListener.java
+++ b/src/java/com/threerings/presents/dobj/OidListListener.java
@@ -1,5 +1,5 @@
 //
-// $Id: OidListListener.java,v 1.1 2001/10/12 00:03:03 mdb Exp $
+// $Id: OidListListener.java,v 1.2 2002/02/03 04:38:05 mdb Exp $
 
 package com.threerings.presents.dobj;
 
@@ -9,7 +9,7 @@ package com.threerings.presents.dobj;
  *
  * @see DObject#addListener
  */
-public interface OidListListener
+public interface OidListListener extends ChangeListener
 {
     /**
      * Called when an object added event has been dispatched on an
diff --git a/src/java/com/threerings/presents/dobj/SetListener.java b/src/java/com/threerings/presents/dobj/SetListener.java
index 48800ad7f..348225a07 100644
--- a/src/java/com/threerings/presents/dobj/SetListener.java
+++ b/src/java/com/threerings/presents/dobj/SetListener.java
@@ -1,5 +1,5 @@
 //
-// $Id: SetListener.java,v 1.1 2001/10/12 00:03:03 mdb Exp $
+// $Id: SetListener.java,v 1.2 2002/02/03 04:38:05 mdb Exp $
 
 package com.threerings.presents.dobj;
 
@@ -9,7 +9,7 @@ package com.threerings.presents.dobj;
  *
  * @see DObject#addListener
  */
-public interface SetListener
+public interface SetListener extends ChangeListener
 {
     /**
      * Called when an element added event has been dispatched on an