diff --git a/src/java/com/threerings/parlor/game/data/GameConfig.java b/src/java/com/threerings/parlor/game/data/GameConfig.java
index 2bee0775..c4720eb4 100644
--- a/src/java/com/threerings/parlor/game/data/GameConfig.java
+++ b/src/java/com/threerings/parlor/game/data/GameConfig.java
@@ -151,12 +151,12 @@ public abstract class GameConfig extends PlaceConfig
     }
 
     @Override
-    public Object clone ()
+    public GameConfig clone ()
     {
         try {
-            return super.clone();
+            return (GameConfig) super.clone();
         } catch (CloneNotSupportedException cnse) {
-            throw new RuntimeException(cnse);
+            throw new AssertionError(cnse);
         }
     }
 }
diff --git a/src/java/com/threerings/parlor/rating/server/RatingDelegate.java b/src/java/com/threerings/parlor/rating/server/RatingDelegate.java
index 666d8330..4a166984 100644
--- a/src/java/com/threerings/parlor/rating/server/RatingDelegate.java
+++ b/src/java/com/threerings/parlor/rating/server/RatingDelegate.java
@@ -420,7 +420,7 @@ public abstract class RatingDelegate extends GameManagerDelegate
                 modified = false;
                 return rating;
             } catch (CloneNotSupportedException cnse) {
-                throw new RuntimeException(cnse);
+                throw new AssertionError(cnse);
             }
         }
 
diff --git a/src/java/com/threerings/puzzle/data/Board.java b/src/java/com/threerings/puzzle/data/Board.java
index 65b2de62..3ebe20a7 100644
--- a/src/java/com/threerings/puzzle/data/Board.java
+++ b/src/java/com/threerings/puzzle/data/Board.java
@@ -48,14 +48,14 @@ public abstract class Board
     public abstract boolean equals (Board other);
 
     @Override
-    public Object clone ()
+    public Board clone ()
     {
         try {
             Board board = (Board)super.clone();
-            board._rando = (BoardRandom)_rando.clone();
+            board._rando = _rando.clone();
             return board;
         } catch (CloneNotSupportedException cnse) {
-            throw new RuntimeException(cnse);
+            throw new AssertionError(cnse);
         }
     }
 
@@ -162,11 +162,11 @@ public abstract class Board
         }
 
         @Override
-        public Object clone () {
+        public BoardRandom clone () {
             try {
-                return super.clone();
+                return (BoardRandom) super.clone();
             } catch (CloneNotSupportedException cnse) {
-                throw new RuntimeException(cnse);
+                throw new AssertionError(cnse);
             }
         }
 
diff --git a/src/java/com/threerings/puzzle/drop/data/DropBoard.java b/src/java/com/threerings/puzzle/drop/data/DropBoard.java
index baca560a..18ffdc3b 100644
--- a/src/java/com/threerings/puzzle/drop/data/DropBoard.java
+++ b/src/java/com/threerings/puzzle/drop/data/DropBoard.java
@@ -687,7 +687,7 @@ public class DropBoard extends Board
     }
 
     @Override
-    public Object clone ()
+    public DropBoard clone ()
     {
         DropBoard board = (DropBoard)super.clone();
         board._board = _board.clone();
diff --git a/src/java/com/threerings/stage/data/StageLocation.java b/src/java/com/threerings/stage/data/StageLocation.java
index 2af905c6..6b002f89 100644
--- a/src/java/com/threerings/stage/data/StageLocation.java
+++ b/src/java/com/threerings/stage/data/StageLocation.java
@@ -74,7 +74,7 @@ public class StageLocation extends SimpleStreamableObject
     // documentation inherited from interface Location
     public Location getOpposite ()
     {
-        StageLocation opp = (StageLocation) clone();
+        StageLocation opp = clone();
         opp.orient = (byte) DirectionUtil.getOpposite(orient);
         return opp;
     }
@@ -113,12 +113,12 @@ public class StageLocation extends SimpleStreamableObject
     }
 
     @Override
-    public Object clone ()
+    public StageLocation clone ()
     {
         try {
-            return super.clone();
+            return (StageLocation) super.clone();
         } catch (CloneNotSupportedException cnse) {
-            throw new RuntimeException(cnse);
+            throw new AssertionError(cnse);
         }
     }
 }
diff --git a/src/java/com/threerings/stage/data/StageScene.java b/src/java/com/threerings/stage/data/StageScene.java
index 898b0b5c..36595b4b 100644
--- a/src/java/com/threerings/stage/data/StageScene.java
+++ b/src/java/com/threerings/stage/data/StageScene.java
@@ -153,7 +153,7 @@ public class StageScene extends SceneImpl
     }
 
     @Override
-    public Object clone ()
+    public StageScene clone ()
         throws CloneNotSupportedException
     {
         // create a new scene with a clone of our model
diff --git a/src/java/com/threerings/stats/data/Stat.java b/src/java/com/threerings/stats/data/Stat.java
index b55eb010..da43330d 100644
--- a/src/java/com/threerings/stats/data/Stat.java
+++ b/src/java/com/threerings/stats/data/Stat.java
@@ -194,12 +194,12 @@ public abstract class Stat
     }
 
     @Override
-    public Object clone ()
+    public Stat clone ()
     {
         try {
-            return super.clone();
-        } catch (Exception e) {
-            throw new RuntimeException("Clone failed", e);
+            return (Stat) super.clone();
+        } catch (CloneNotSupportedException e) {
+            throw new AssertionError(e);
         }
     }
 
diff --git a/src/java/com/threerings/whirled/data/AuxModel.java b/src/java/com/threerings/whirled/data/AuxModel.java
index 9f881a74..2cf85692 100644
--- a/src/java/com/threerings/whirled/data/AuxModel.java
+++ b/src/java/com/threerings/whirled/data/AuxModel.java
@@ -31,6 +31,6 @@ public interface AuxModel extends Streamable, Cloneable
     /**
      * Creates a clone of this auxiliary model.
      */
-    public Object clone ()
+    public AuxModel clone ()
         throws CloneNotSupportedException;
 }
diff --git a/src/java/com/threerings/whirled/data/SceneModel.java b/src/java/com/threerings/whirled/data/SceneModel.java
index b1f7c4c1..859d26f1 100644
--- a/src/java/com/threerings/whirled/data/SceneModel.java
+++ b/src/java/com/threerings/whirled/data/SceneModel.java
@@ -61,13 +61,13 @@ public class SceneModel extends SimpleStreamableObject
     }
 
     @Override
-    public Object clone ()
+    public SceneModel clone ()
         throws CloneNotSupportedException
     {
         SceneModel model = (SceneModel)super.clone();
         model.auxModels = new AuxModel[auxModels.length];
         for (int ii = 0; ii < auxModels.length; ii++) {
-            model.auxModels[ii] = (AuxModel)auxModels[ii].clone();
+            model.auxModels[ii] = auxModels[ii].clone();
         }
         return model;
     }
diff --git a/src/java/com/threerings/whirled/spot/data/Location.java b/src/java/com/threerings/whirled/spot/data/Location.java
index 7f4ca3c1..12891761 100644
--- a/src/java/com/threerings/whirled/spot/data/Location.java
+++ b/src/java/com/threerings/whirled/spot/data/Location.java
@@ -51,5 +51,5 @@ public interface Location extends Streamable, Cloneable
     /**
      * Locations are cloneable.
      */
-    public Object clone ();
+    public Location clone ();
 }
diff --git a/src/java/com/threerings/whirled/spot/data/Portal.java b/src/java/com/threerings/whirled/spot/data/Portal.java
index 864931fc..b389ed55 100644
--- a/src/java/com/threerings/whirled/spot/data/Portal.java
+++ b/src/java/com/threerings/whirled/spot/data/Portal.java
@@ -57,7 +57,7 @@ public class Portal extends SimpleStreamableObject
      */
     public Location getLocation ()
     {
-        return (Location) loc.clone();
+        return loc.clone();
     }
 
     /**
@@ -85,12 +85,12 @@ public class Portal extends SimpleStreamableObject
     }
 
     @Override
-    public Object clone ()
+    public Portal clone ()
     {
         try {
-            return super.clone();
+            return (Portal) super.clone();
         } catch (CloneNotSupportedException cnse) {
-            throw new RuntimeException(cnse);
+            throw new AssertionError(cnse);
         }
     }
 
diff --git a/src/java/com/threerings/whirled/spot/data/SpotSceneModel.java b/src/java/com/threerings/whirled/spot/data/SpotSceneModel.java
index b2d5955a..5db7d152 100644
--- a/src/java/com/threerings/whirled/spot/data/SpotSceneModel.java
+++ b/src/java/com/threerings/whirled/spot/data/SpotSceneModel.java
@@ -64,14 +64,14 @@ public class SpotSceneModel extends SimpleStreamableObject
     }
 
     @Override
-    public Object clone ()
+    public SpotSceneModel clone ()
         throws CloneNotSupportedException
     {
         SpotSceneModel model = (SpotSceneModel)super.clone();
         // clone our portals individually
         model.portals = new Portal[portals.length];
         for (int ii = 0, ll = portals.length; ii < ll; ii++) {
-            model.portals[ii] = (Portal)portals[ii].clone();
+            model.portals[ii] = portals[ii].clone();
         }
         return model;
     }