diff --git a/Engine.Core/Helpers/Event.cs b/Engine.Core/Helpers/Event.cs
index de869ff..1186593 100644
--- a/Engine.Core/Helpers/Event.cs
+++ b/Engine.Core/Helpers/Event.cs
@@ -206,7 +206,7 @@ public class Event
 /// 
 /// </summary>
 /// <typeparam name="TSender">Sender type</typeparam>
-public class Event<TSender>
+public class Event<TSender> where TSender : class
 {
     // We use Ascending order because draw calls are running from last to first
     private static readonly Comparer<ListenerData> SortByAscendingPriority = Comparer<ListenerData>.Create((x, y) => x.Priority.CompareTo(y.Priority));
@@ -375,7 +375,7 @@ public class Event<TSender>
 /// 
 /// </summary>
 /// <typeparam name="TSender">Sender type</typeparam>
-public class Event<TSender, TArguments>
+public class Event<TSender, TArguments> where TSender : class
 {
     // We use Ascending order because draw calls are running from last to first
     private static readonly Comparer<ListenerData> SortByAscendingPriority = Comparer<ListenerData>.Create((x, y) => x.Priority.CompareTo(y.Priority));