diff --git a/server/gameserver/roomobstacle.cc b/server/gameserver/roomobstacle.cc
index a0e29b8..ff54bbe 100644
--- a/server/gameserver/roomobstacle.cc
+++ b/server/gameserver/roomobstacle.cc
@@ -131,6 +131,10 @@ void RoomObstacle::ActiveTimerFunc()
 
 void RoomObstacle::UpdateTimerFunc()
 {
+    if (!grid_list_) {
+        grid_list_ = new std::set<GridCell*>();
+        room->grid_service->GetAllCellsByXy(room, GetPos().x, GetPos().y, *grid_list_);
+    }
     if (grid_list_ && master.Get() && !IsDead(room)) {
         std::set<Human*> human_list;
         room->grid_service->TraverseAllLayerHumanList