diff --git a/src/java/com/threerings/media/tile/SwissArmyTileSet.java b/src/java/com/threerings/media/tile/SwissArmyTileSet.java
index 005bcdd41..a572d8feb 100644
--- a/src/java/com/threerings/media/tile/SwissArmyTileSet.java
+++ b/src/java/com/threerings/media/tile/SwissArmyTileSet.java
@@ -1,5 +1,5 @@
 //
-// $Id: SwissArmyTileSet.java,v 1.9 2003/01/13 22:49:46 mdb Exp $
+// $Id: SwissArmyTileSet.java,v 1.10 2003/01/15 09:11:37 mdb Exp $
 
 package com.threerings.media.tile;
 
@@ -184,4 +184,8 @@ public class SwissArmyTileSet extends TileSet
     /** The distance (x, y) in pixels between each tile in each row
      * horizontally, and between each row of tiles vertically.  */
     protected Dimension _gapSize = new Dimension();
+
+    /** Increase this value when object's serialized state is impacted by
+     * a class change (modification of fields, inheritance). */
+    private static final long serialVersionUID = 1;
 }
diff --git a/src/java/com/threerings/miso/tile/BaseTileSet.java b/src/java/com/threerings/miso/tile/BaseTileSet.java
index 7c80252b2..77758df0b 100644
--- a/src/java/com/threerings/miso/tile/BaseTileSet.java
+++ b/src/java/com/threerings/miso/tile/BaseTileSet.java
@@ -1,5 +1,5 @@
 //
-// $Id: BaseTileSet.java,v 1.11 2003/01/13 22:55:12 mdb Exp $
+// $Id: BaseTileSet.java,v 1.12 2003/01/15 09:11:37 mdb Exp $
 
 package com.threerings.miso.tile;
 
@@ -49,4 +49,8 @@ public class BaseTileSet extends SwissArmyTileSet
 
     /** Whether each tile is passable. */
     protected boolean[] _passable;
+
+    /** Increase this value when object's serialized state is impacted by
+     * a class change (modification of fields, inheritance). */
+    private static final long serialVersionUID = 1;
 }