diff --git a/packages/topdown/tiles.js b/packages/topdown/tiles.js
index acd5b21..c356ff9 100644
--- a/packages/topdown/tiles.js
+++ b/packages/topdown/tiles.js
@@ -96,8 +96,7 @@ export class Tiles extends decorate(class {}) {
   }
 
   tick(elapsed) {
-    this._sizeState = this._sizeState.set(0, this.width);
-    this._sizeState = this._sizeState.set(1, this.height);
+    this._sizeState = this._sizeState.set(0, this.width).set(1, this.height);
     this._state = this._state.set('size', this._sizeState);
     this._state = this._state.set('data', this.data);
   }