diff --git a/OpenRa.Game/Sidebar.cs b/OpenRa.Game/Sidebar.cs
index d316ed6669..0c148f2052 100644
--- a/OpenRa.Game/Sidebar.cs
+++ b/OpenRa.Game/Sidebar.cs
@@ -32,7 +32,7 @@ namespace OpenRa.Game
 		public Sidebar( Race race, Renderer renderer, Game game )
 		{
 			this.techTree = game.LocalPlayer.TechTree;
-			this.techTree.BuildableItemsChanged += (sender, e) => { PopulateItemList(); };
+            this.techTree.BuildableItemsChanged += PopulateItemList;
 			this.game = game;
 			region = GRegion.Create(game.viewport, DockStyle.Right, 128, Paint, MouseHandler);
 			game.viewport.AddRegion( region );
@@ -99,8 +99,6 @@ namespace OpenRa.Game
 
 		void Paint()
 		{
-//			PopulateItemList();	// todo: do this less often, just when things actually change!
-
 			foreach (SidebarItem i in items)
 				i.Paint(spriteRenderer, region.Location);
 
diff --git a/OpenRa.Game/TechTree/TechTree.cs b/OpenRa.Game/TechTree/TechTree.cs
index f38c4b2935..24840ed8e4 100644
--- a/OpenRa.Game/TechTree/TechTree.cs
+++ b/OpenRa.Game/TechTree/TechTree.cs
@@ -102,7 +102,7 @@ namespace OpenRa.TechTree
 					changed = true;
 			}
 
-			if (changed) BuildableItemsChanged(this, EventArgs.Empty);
+			if (changed) BuildableItemsChanged();
 		}
 
 		public IEnumerable<Item> BuildableItems
@@ -115,6 +115,6 @@ namespace OpenRa.TechTree
 			}
 		}
 
-		public event EventHandler BuildableItemsChanged = (sender, e) => { };
+		public event Action BuildableItemsChanged = () => { };
 	}
 }