diff --git a/src/Add-on/Viewport/OneKeyLayout.ts b/src/Add-on/Viewport/OneKeyLayout.ts
index 9da2bd279..60be3a9b2 100644
--- a/src/Add-on/Viewport/OneKeyLayout.ts
+++ b/src/Add-on/Viewport/OneKeyLayout.ts
@@ -558,16 +558,14 @@ export class OneKeyLayout implements Command
         return vpInfos;
     };
 
-    private checkBoxOnY(firstBox: Box3Ext, box: Box3Ext, boxBoardMap: Map<Box3Ext, (Board | CompositeEntity | SweepSolid)[]>)
+    private checkBoxOnY(firstBox: Box3Ext, box: Box3Ext, boxBoardMap: Map<Box3Ext, Entity[]>)
     {
         if (firstBox.min.x > box.max.x || firstBox.max.x < box.min.x)
             return false;
         else
         {
-            (boxBoardMap.get(box) as Entity[]).forEach((br) =>
-            {
-                (boxBoardMap.get(firstBox) as Entity[]).push(br);
-            });
+            for (let br of boxBoardMap.get(box))
+                boxBoardMap.get(firstBox).push(br);
             firstBox.union(box);
             boxBoardMap.delete(box);
             return true;