diff --git a/server/gameserver/bullet.cc b/server/gameserver/bullet.cc
index c7f9a5ac..b4d13356 100644
--- a/server/gameserver/bullet.cc
+++ b/server/gameserver/bullet.cc
@@ -451,6 +451,7 @@ void Bullet::Check(float distance)
                 } else if (obstacle->meta->i->thing_type() == kObstacleStrengthenWall) {
                     if (!strengthened_ && TestCollision(room, collider)) {
                         strengthened_ = true;
+                        OnStrengthen(obstacle);
                     }
                 }
             }
@@ -745,3 +746,8 @@ void Bullet::CalcDmg(Entity* entity,
         finaly_dmg = std::max(finaly_dmg, 0.0f);
     }
 }
+
+void Bullet::OnStrengthen(Obstacle* ob)
+{
+
+}
diff --git a/server/gameserver/bullet.h b/server/gameserver/bullet.h
index dcf9745c..1aada2e7 100644
--- a/server/gameserver/bullet.h
+++ b/server/gameserver/bullet.h
@@ -67,6 +67,7 @@ protected:
     void Check(float distance);
     void AddGunBuff();
     void OnKillTarget(Entity* target);
+    void OnStrengthen(Obstacle* ob);
 
 private:
     CircleCollider* self_collider_ = nullptr;