diff --git a/src/game.rs b/src/game.rs
index 1327d86..2253b84 100644
--- a/src/game.rs
+++ b/src/game.rs
@@ -448,21 +448,15 @@ impl Game {
 
             if room.palette_id.is_some()  {
                 let key = room.palette_id.clone().unwrap();
-                if palette_id_changes.contains_key(&key) {
-                    let new_id = palette_id_changes.get(&key).unwrap();
-                    room.palette_id = Some(new_id.clone());
+                let change = palette_id_changes.get(&key);
+                if change.is_some() {
+                    room.palette_id = Some(change.unwrap().clone());
                 }
             }
 
-            let mut tiles = Vec::new();
-            for tile_id in &room.tiles {
-                tiles.push(if tile_id_changes.contains_key(tile_id) {
-                    tile_id_changes.get(tile_id).unwrap()
-                } else {
-                    tile_id
-                }.clone());
-            }
-            room.tiles = tiles;
+            room.tiles = room.tiles.iter().map(|tile_id|
+                tile_id_changes.get(tile_id).unwrap_or(tile_id).clone()
+            ).collect();
 
             room.items = room.items.iter().map(|instance|
                 if item_id_changes.contains_key(&instance.id) {
@@ -672,7 +666,9 @@ impl Game {
     #[inline]
     pub fn add_palette(&mut self, mut palette: Palette) -> String {
         let new_id = try_id(self.palette_ids(), palette.id.clone());
-        palette.id = new_id.clone();
+        if new_id != palette.id {
+            palette.id = new_id.clone();
+        }
         self.palettes.push(palette);
         new_id
     }
@@ -680,17 +676,24 @@ impl Game {
     /// adds a tile safely and returns the new tile ID
     #[inline]
     pub fn add_tile(&mut self, mut tile: Tile) -> String {
-        let new_id = self.new_tile_id();
-        tile.id = new_id.clone();
+        if self.tile_ids().contains(&tile.id) {
+            let new_id = self.new_tile_id();
+            if new_id != tile.id {
+                tile.id = new_id;
+            }
+        }
+        let id = tile.id.clone();
         self.tiles.push(tile);
-        new_id
+        id
     }
 
     /// adds a sprite safely and returns the new sprite ID
     #[inline]
     pub fn add_sprite(&mut self, mut sprite: Sprite) -> String {
         let new_id = try_id(self.sprite_ids(), sprite.id.clone());
-        sprite.id = new_id.clone();
+        if new_id != sprite.id {
+            sprite.id = new_id.clone();
+        }
         self.sprites.push(sprite);
         new_id
     }