diff --git a/src/java/com/threerings/presents/client/ClientDObjectMgr.java b/src/java/com/threerings/presents/client/ClientDObjectMgr.java
index e94040e00..258a0b169 100644
--- a/src/java/com/threerings/presents/client/ClientDObjectMgr.java
+++ b/src/java/com/threerings/presents/client/ClientDObjectMgr.java
@@ -1,5 +1,5 @@
 //
-// $Id: ClientDObjectMgr.java,v 1.24 2003/05/22 17:23:53 mdb Exp $
+// $Id: ClientDObjectMgr.java,v 1.25 2003/08/16 04:14:56 mdb Exp $
 
 package com.threerings.presents.client;
 
@@ -74,7 +74,12 @@ public class ClientDObjectMgr
     // inherit documentation from the interface
     public void subscribeToObject (int oid, Subscriber target)
     {
-        queueAction(oid, target, true);
+        if (oid <= 0) {
+            target.requestFailed(
+                oid, new ObjectAccessException("Invalid oid " + oid + "."));
+        } else {
+            queueAction(oid, target, true);
+        }
     }
 
     // inherit documentation from the interface
diff --git a/src/java/com/threerings/presents/server/PresentsDObjectMgr.java b/src/java/com/threerings/presents/server/PresentsDObjectMgr.java
index 7945a5187..66ab11479 100644
--- a/src/java/com/threerings/presents/server/PresentsDObjectMgr.java
+++ b/src/java/com/threerings/presents/server/PresentsDObjectMgr.java
@@ -1,5 +1,5 @@
 //
-// $Id: PresentsDObjectMgr.java,v 1.36 2003/08/15 18:50:02 mdb Exp $
+// $Id: PresentsDObjectMgr.java,v 1.37 2003/08/16 04:14:56 mdb Exp $
 
 package com.threerings.presents.server;
 
@@ -77,9 +77,14 @@ public class PresentsDObjectMgr
     // inherit documentation from the interface
     public void subscribeToObject (int oid, Subscriber target)
     {
-        // queue up an access object event
-        postEvent(new AccessObjectEvent(oid, target,
-                                        AccessObjectEvent.SUBSCRIBE));
+        if (oid <= 0) {
+            target.requestFailed(
+                oid, new ObjectAccessException("Invalid oid " + oid + "."));
+        } else {
+            // queue up an access object event
+            postEvent(new AccessObjectEvent(
+                          oid, target, AccessObjectEvent.SUBSCRIBE));
+        }
     }
 
     // inherit documentation from the interface
@@ -659,6 +664,11 @@ public class PresentsDObjectMgr
             _target = target;
         }
 
+        public boolean isPrivate ()
+        {
+            return true;
+        }
+
         public boolean applyToObject (DObject target)
             throws ObjectAccessException
         {
@@ -731,6 +741,11 @@ public class PresentsDObjectMgr
             _action = action;
         }
 
+        public boolean isPrivate ()
+        {
+            return true;
+        }
+
         public boolean applyToObject (DObject target)
             throws ObjectAccessException
         {