diff --git a/src/java/com/threerings/crowd/client/LocationDirector.java b/src/java/com/threerings/crowd/client/LocationDirector.java
index ef10f2d08..7d7e8b749 100644
--- a/src/java/com/threerings/crowd/client/LocationDirector.java
+++ b/src/java/com/threerings/crowd/client/LocationDirector.java
@@ -1,5 +1,5 @@
 //
-// $Id: LocationDirector.java,v 1.30 2003/06/14 00:47:16 mdb Exp $
+// $Id: LocationDirector.java,v 1.31 2003/10/03 20:41:31 mdb Exp $
 
 package com.threerings.crowd.client;
 
@@ -112,6 +112,12 @@ public class LocationDirector extends BasicDirector
      */
     public boolean moveTo (int placeId)
     {
+        // make sure the placeId is valid
+        if (placeId < 0) {
+            Log.warning("Refusing moveTo(): invalid placeId " + placeId + ".");
+            return false;
+        }
+
         // first check to see if our observers are happy with this move
         // request
         if (!mayMoveTo(placeId, null)) {
diff --git a/src/java/com/threerings/whirled/client/SceneDirector.java b/src/java/com/threerings/whirled/client/SceneDirector.java
index 182d7ea32..18cdd0d3a 100644
--- a/src/java/com/threerings/whirled/client/SceneDirector.java
+++ b/src/java/com/threerings/whirled/client/SceneDirector.java
@@ -1,5 +1,5 @@
 //
-// $Id: SceneDirector.java,v 1.24 2003/02/12 07:23:30 mdb Exp $
+// $Id: SceneDirector.java,v 1.25 2003/10/03 20:41:31 mdb Exp $
 
 package com.threerings.whirled.client;
 
@@ -94,6 +94,12 @@ public class SceneDirector extends BasicDirector
      */
     public boolean moveTo (int sceneId)
     {
+        // make sure the sceneId is valid
+        if (sceneId < 0) {
+            Log.warning("Refusing moveTo(): invalid sceneId " + sceneId + ".");
+            return false;
+        }
+
         // sanity-check the destination scene id
         if (sceneId == _sceneId) {
             Log.warning("Refusing request to move to the same scene " +
diff --git a/src/java/com/threerings/whirled/zone/client/ZoneDirector.java b/src/java/com/threerings/whirled/zone/client/ZoneDirector.java
index 0d0598bc5..17d8d01d1 100644
--- a/src/java/com/threerings/whirled/zone/client/ZoneDirector.java
+++ b/src/java/com/threerings/whirled/zone/client/ZoneDirector.java
@@ -1,5 +1,5 @@
 //
-// $Id: ZoneDirector.java,v 1.14 2003/02/12 07:23:32 mdb Exp $
+// $Id: ZoneDirector.java,v 1.15 2003/10/03 20:41:32 mdb Exp $
 
 package com.threerings.whirled.zone.client;
 
@@ -94,6 +94,13 @@ public class ZoneDirector extends BasicDirector
      */
     public boolean moveTo (int zoneId, int sceneId, ResultListener rl)
     {
+        // make sure the zoneId and sceneId are valid
+        if (zoneId < 0 || sceneId < 0) {
+            Log.warning("Refusing moveTo(): invalid sceneId or zoneId " +
+                        "[zoneId=" + zoneId + ", sceneId=" + sceneId + "].");
+            return false;
+        }
+
         // if the requested zone is the same as our current zone, we just
         // want a regular old moveTo request
         if (_summary != null && zoneId == _summary.zoneId) {