diff --git a/Engine.Core/Abstract/Assignable/IHierarchyObject.cs b/Engine.Core/Abstract/Assignable/IHierarchyObject.cs
index be67532..04308a0 100644
--- a/Engine.Core/Abstract/Assignable/IHierarchyObject.cs
+++ b/Engine.Core/Abstract/Assignable/IHierarchyObject.cs
@@ -20,7 +20,7 @@ public interface IHierarchyObject : IEntity, INameable
     /// <summary>
     /// Gets the <see cref="IGameManager"/> associated with this <see cref="IEntity"/> , if any.
     /// </summary>
-    IGameManager? GameManager { get; }
+    IGameManager GameManager { get; }
 
     /// <summary>
     /// Indicates whether the <see cref="IEntity"/> is currently in the hierarchy.
diff --git a/Engine.Core/Behaviour.cs b/Engine.Core/Behaviour.cs
index a16cea0..13d1117 100644
--- a/Engine.Core/Behaviour.cs
+++ b/Engine.Core/Behaviour.cs
@@ -6,6 +6,7 @@ public abstract class Behaviour : BehaviourBase
 {
     private bool isInitializedThisFrame = false;
 
+    protected IGameManager GameManager => BehaviourController.GameObject.GameManager;
     protected IGameObject GameObject => BehaviourController.GameObject;
     protected ITransform Transform => BehaviourController.GameObject.Transform;
 
@@ -33,7 +34,7 @@ public abstract class Behaviour : BehaviourBase
         OnInitialize();
 
         if (GameObject.IsInHierarchy)
-            EnteredHierarchy(GameObject, GameObject.GameManager ?? throw new System.Exception("Unexpected Error"));
+            EnteredHierarchy(GameObject, GameManager);
     }
 
     protected virtual void OnFinalize() { }
@@ -48,7 +49,7 @@ public abstract class Behaviour : BehaviourBase
         OnFinalize();
 
         if (GameObject.IsInHierarchy)
-            ExitedHierarchy(GameObject, GameObject.GameManager ?? throw new System.Exception("Unexpected Error"));
+            ExitedHierarchy(GameObject, GameManager);
     }
 
     protected virtual void OnPreUpdatePreActiveCheck() { }
diff --git a/Engine.Core/GameObject.cs b/Engine.Core/GameObject.cs
index 942ed15..8f2a9af 100644
--- a/Engine.Core/GameObject.cs
+++ b/Engine.Core/GameObject.cs
@@ -18,13 +18,13 @@ public class GameObject : BaseEntity, IGameObject
 
     private ITransform _transform = null!;
     private IBehaviourController _behaviourController = null!;
-    private IGameManager? _gameManager = null;
+    private IGameManager _gameManager = null!;
 
     private string _name = nameof(GameObject);
 
     public ITransform Transform => _transform;
     public IBehaviourController BehaviourController => _behaviourController;
-    public IGameManager? GameManager => _gameManager;
+    public IGameManager GameManager => _gameManager;
     public bool IsInHierarchy => GameManager is not null;
 
     public string Name
@@ -144,7 +144,7 @@ public class GameObject : BaseEntity, IGameObject
         if (!IsInHierarchy || _gameManager is not IGameManager gameManager)
             return false;
 
-        _gameManager = null;
+        _gameManager = null!;
         OnExitedHierarchy?.Invoke(this, gameManager);
         return true;
     }
diff --git a/Engine.Core/HierarchyObjectBase.cs b/Engine.Core/HierarchyObjectBase.cs
index 9400f43..df5a253 100644
--- a/Engine.Core/HierarchyObjectBase.cs
+++ b/Engine.Core/HierarchyObjectBase.cs
@@ -17,9 +17,9 @@ public abstract class HierarchyObjectBase : IHierarchyObject
     private string _name = nameof(HierarchyObjectBase);
     private bool _initialized = false;
     private IStateEnable _stateEnable = null!;
-    private IGameManager? _gameManager = null;
+    private IGameManager _gameManager = null!;
 
-    public IGameManager? GameManager => _gameManager;
+    public IGameManager GameManager => _gameManager;
 
     public bool IsInHierarchy => _gameManager is not null;