diff --git a/OpenRA.Game/Primitives/Rectangle.cs b/OpenRA.Game/Primitives/Rectangle.cs
index 91a721feb6..8dc8c65a8f 100644
--- a/OpenRA.Game/Primitives/Rectangle.cs
+++ b/OpenRA.Game/Primitives/Rectangle.cs
@@ -13,13 +13,12 @@ using System;
 
 namespace OpenRA.Primitives
 {
-	public struct Rectangle : IEquatable<Rectangle>
+	public readonly struct Rectangle : IEquatable<Rectangle>
 	{
-		// TODO: Make these readonly: this will require a lot of changes to the UI logic
-		public int X;
-		public int Y;
-		public int Width;
-		public int Height;
+		public readonly int X;
+		public readonly int Y;
+		public readonly int Width;
+		public readonly int Height;
 		public static readonly Rectangle Empty;
 
 		public static Rectangle FromLTRB(int left, int top, int right, int bottom)