diff --git a/OpenRA.Game/OpenRA.Game.csproj b/OpenRA.Game/OpenRA.Game.csproj
index 2832ef2ba7..2271cc2038 100644
--- a/OpenRA.Game/OpenRA.Game.csproj
+++ b/OpenRA.Game/OpenRA.Game.csproj
@@ -289,7 +289,6 @@
     <Compile Include="Primitives\ObservableDictionary.cs" />
     <Compile Include="Primitives\Pair.cs" />
     <Compile Include="Primitives\PriorityQueue.cs" />
-    <Compile Include="Primitives\Set.cs" />
     <Compile Include="Support\Log.cs" />
     <Compile Include="Support\PerfTimer.cs" />
     <Compile Include="Exts.cs" />
diff --git a/OpenRA.Game/Primitives/Set.cs b/OpenRA.Game/Primitives/Set.cs
deleted file mode 100755
index 43c76648eb..0000000000
--- a/OpenRA.Game/Primitives/Set.cs
+++ /dev/null
@@ -1,56 +0,0 @@
-#region Copyright & License Information
-/*
- * Copyright 2007-2011 The OpenRA Developers (see AUTHORS)
- * This file is part of OpenRA, which is free software. It is made
- * available to you under the terms of the GNU General Public License
- * as published by the Free Software Foundation. For more information,
- * see COPYING.
- */
-#endregion
-
-using System;
-using System.Collections;
-using System.Collections.Generic;
-
-namespace OpenRA.Primitives
-{
-	public class Set<T> : IEnumerable<T>
-	{
-		Dictionary<T, bool> data = new Dictionary<T, bool>();
-
-		public void Add( T obj )
-		{
-			data.Add( obj, false );
-			if( OnAdd != null )
-				OnAdd( obj );
-		}
-
-		public void Remove( T obj )
-		{
-			data.Remove( obj );
-			if( OnRemove != null )
-				OnRemove( obj );
-		}
-
-		public event Action<T> OnAdd;
-		public event Action<T> OnRemove;
-
-		public IEnumerator<T> GetEnumerator()
-		{
-			return data.Keys.GetEnumerator();
-		}
-
-		IEnumerator IEnumerable.GetEnumerator()
-		{
-			return GetEnumerator();
-		}
-
-		public bool Contains( T obj ) { return data.ContainsKey(obj); }
-
-		public Set( params T[] ts )
-		{
-			foreach( var t in ts )
-				Add(t);
-		}
-	}
-}
diff --git a/OpenRA.Game/World.cs b/OpenRA.Game/World.cs
index 1d1d12213a..09edb42db5 100644
--- a/OpenRA.Game/World.cs
+++ b/OpenRA.Game/World.cs
@@ -27,7 +27,7 @@ namespace OpenRA
 	public class World
 	{
 		internal TraitDictionary traitDict = new TraitDictionary();
-		Set<Actor> actors = new Set<Actor>();
+		HashSet<Actor> actors = new HashSet<Actor>();
 		List<IEffect> effects = new List<IEffect>();
 		Queue<Action<World>> frameEndActions = new Queue<Action<World>>();