diff --git a/.editorconfig b/.editorconfig
index e57b39688c..ca3fee44ad 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -830,6 +830,9 @@ dotnet_diagnostic.CA5351.severity = warning
 ### Usage Rules
 ### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/usage-warnings
 
+# Call GC.SuppressFinalize correctly.
+dotnet_diagnostic.CA1816.severity = warning
+
 # Rethrow to preserve stack details.
 dotnet_diagnostic.CA2200.severity = warning
 
diff --git a/OpenRA.Game/Graphics/SpriteCache.cs b/OpenRA.Game/Graphics/SpriteCache.cs
index bbe6bd3403..c981b5e342 100644
--- a/OpenRA.Game/Graphics/SpriteCache.cs
+++ b/OpenRA.Game/Graphics/SpriteCache.cs
@@ -18,7 +18,7 @@ using OpenRA.Primitives;
 
 namespace OpenRA.Graphics
 {
-	public class SpriteCache : IDisposable
+	public sealed class SpriteCache : IDisposable
 	{
 		public readonly Dictionary<SheetType, SheetBuilder> SheetBuilders;
 		readonly ISpriteLoader[] loaders;
diff --git a/OpenRA.Game/Manifest.cs b/OpenRA.Game/Manifest.cs
index 01d8106164..d9739f7585 100644
--- a/OpenRA.Game/Manifest.cs
+++ b/OpenRA.Game/Manifest.cs
@@ -65,7 +65,7 @@ namespace OpenRA
 	}
 
 	/// <summary>Describes what is to be loaded in order to run a mod.</summary>
-	public class Manifest : IDisposable
+	public sealed class Manifest : IDisposable
 	{
 		public readonly string Id;
 		public readonly IReadOnlyPackage Package;
diff --git a/OpenRA.Game/Map/Map.cs b/OpenRA.Game/Map/Map.cs
index 4b51221224..9315665f1b 100644
--- a/OpenRA.Game/Map/Map.cs
+++ b/OpenRA.Game/Map/Map.cs
@@ -149,7 +149,7 @@ namespace OpenRA
 		}
 	}
 
-	public class Map : IReadOnlyFileSystem, IDisposable
+	public sealed class Map : IReadOnlyFileSystem, IDisposable
 	{
 		public const int SupportedMapFormat = 11;
 		public const int CurrentMapFormat = 12;
diff --git a/OpenRA.Game/Map/MapPreview.cs b/OpenRA.Game/Map/MapPreview.cs
index cdfa253ea9..e38def96ac 100644
--- a/OpenRA.Game/Map/MapPreview.cs
+++ b/OpenRA.Game/Map/MapPreview.cs
@@ -61,7 +61,7 @@ namespace OpenRA
 		public readonly int mapformat;
 	}
 
-	public class MapPreview : IDisposable, IReadOnlyFileSystem
+	public sealed class MapPreview : IDisposable, IReadOnlyFileSystem
 	{
 		/// <summary>Wrapper that enables map data to be replaced in an atomic fashion.</summary>
 		sealed class InnerData
diff --git a/OpenRA.Mods.Cnc/Graphics/VoxelModelSequenceLoader.cs b/OpenRA.Mods.Cnc/Graphics/VoxelModelSequenceLoader.cs
index e128d579e7..5d45e236e4 100644
--- a/OpenRA.Mods.Cnc/Graphics/VoxelModelSequenceLoader.cs
+++ b/OpenRA.Mods.Cnc/Graphics/VoxelModelSequenceLoader.cs
@@ -48,7 +48,7 @@ namespace OpenRA.Mods.Cnc.Graphics
 		}
 	}
 
-	public class VoxelModelCache : IModelCache
+	public sealed class VoxelModelCache : IModelCache
 	{
 		readonly VoxelLoader loader;
 		readonly Dictionary<string, Dictionary<string, IModel>> models = new();