diff --git a/include/game/World.h b/include/game/World.h
index d3f4fa7..e54af27 100644
--- a/include/game/World.h
+++ b/include/game/World.h
@@ -203,12 +203,12 @@ public:
 
     // WorldListener
 
-    virtual void OnArcherTowerShot(MobPtr target, ArcherTower* shooter){}
+    virtual void OnArcherTowerShot(MobPtr target, ArcherTower* shooter);
 
-    virtual void OnArrowShot(MobPtr target, Tower* shooter){}
-    virtual void OnExplosion(utils::shape::Circle explosion, float centerDamage, Tower* shooter){}
+    virtual void OnArrowShot(MobPtr target, Tower* shooter);
+    virtual void OnExplosion(utils::shape::Circle explosion, float centerDamage, Tower* shooter);
 
-    virtual void OnMobDamage(MobPtr target, float damage, Tower* source){}
+    virtual void OnMobDamage(MobPtr target, float damage, Tower* source);
 private:
     void moveMobs(std::uint64_t delta);
     void moveMob(MobPtr mob, std::uint64_t delta);