diff --git a/server/gameserver/roomobstacle.cc b/server/gameserver/roomobstacle.cc
index 1e79d25..cd26ebd 100644
--- a/server/gameserver/roomobstacle.cc
+++ b/server/gameserver/roomobstacle.cc
@@ -715,18 +715,20 @@ void RoomObstacle::InstallPreExplostionSummonTimer()
                      [] (const a8::XParams& param)
                      {
                          RoomObstacle* obstacle = (RoomObstacle*)param.sender.GetUserData();
-                         obstacle->room->CreateObstacle
+                         RoomObstacle* p = obstacle->room->CreateObstacle
                              (
                               param.param1,
                               obstacle->GetPos().x + param.param2.GetDouble(),
                               obstacle->GetPos().y + param.param3.GetDouble()
                               );
-                         obstacle->Active();
+                         if (p) {
+                             p->Active();
+                         }
                      },
                      &xtimer_attacher.timer_list_
                      );
             }//end for tuple
+            base_time += meta->i->explosion_interval();
         }
-        base_time += meta->i->explosion_interval();
     }
 }