diff --git a/server/gameserver/roomobstacle.cc b/server/gameserver/roomobstacle.cc
index 99ad184..eeeb644 100644
--- a/server/gameserver/roomobstacle.cc
+++ b/server/gameserver/roomobstacle.cc
@@ -193,7 +193,7 @@ void RoomObstacle::SpecExplosion()
                                          meta->i->explosion_effect(),
                                          meta->i->damage()
                                          );
-            {
+            if (master.Get()) {
                 std::set<Human*> human_list;
                 room->grid_service->TraverseAllLayerHumanList
                     (room->GetRoomIdx(),