diff --git a/OpenRA.Mods.Common/UtilityCommands/ImportLegacyMapCommand.cs b/OpenRA.Mods.Cnc/UtilityCommands/ImportGen1MapCommand.cs
similarity index 95%
rename from OpenRA.Mods.Common/UtilityCommands/ImportLegacyMapCommand.cs
rename to OpenRA.Mods.Cnc/UtilityCommands/ImportGen1MapCommand.cs
index 70949644de..93066b32c3 100644
--- a/OpenRA.Mods.Common/UtilityCommands/ImportLegacyMapCommand.cs
+++ b/OpenRA.Mods.Cnc/UtilityCommands/ImportGen1MapCommand.cs
@@ -15,19 +15,20 @@ using System.IO;
 using System.Linq;
 using System.Text;
 using OpenRA.FileSystem;
+using OpenRA.Mods.Common;
 using OpenRA.Mods.Common.FileFormats;
 using OpenRA.Mods.Common.Terrain;
 using OpenRA.Mods.Common.Traits;
 using OpenRA.Primitives;
 using OpenRA.Traits;
 
-namespace OpenRA.Mods.Common.UtilityCommands
+namespace OpenRA.Mods.Cnc.UtilityCommands
 {
-	public abstract class ImportLegacyMapCommand
+	public abstract class ImportGen1MapCommand
 	{
 		public readonly int MapSize;
 
-		protected ImportLegacyMapCommand(int mapSize)
+		protected ImportGen1MapCommand(int mapSize)
 		{
 			MapSize = mapSize;
 		}
@@ -451,4 +452,22 @@ namespace OpenRA.Mods.Common.UtilityCommands
 			}
 		}
 	}
+
+#if !NET6_0_OR_GREATER
+	public static class Extensions
+	{
+		/// <summary>
+		/// Only used for Mono builds. .NET 6 added the exact same thing.
+		/// </summary>
+		public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
+		{
+			var knownKeys = new HashSet<TKey>();
+			foreach (var element in source)
+			{
+				if (knownKeys.Add(keySelector(element)))
+					yield return element;
+			}
+		}
+	}
+#endif
 }
diff --git a/OpenRA.Mods.Cnc/UtilityCommands/ImportRedAlertLegacyMapCommand.cs b/OpenRA.Mods.Cnc/UtilityCommands/ImportRedAlertMapCommand.cs
similarity index 97%
rename from OpenRA.Mods.Cnc/UtilityCommands/ImportRedAlertLegacyMapCommand.cs
rename to OpenRA.Mods.Cnc/UtilityCommands/ImportRedAlertMapCommand.cs
index 8e283a2bba..4d6b0ca813 100644
--- a/OpenRA.Mods.Cnc/UtilityCommands/ImportRedAlertLegacyMapCommand.cs
+++ b/OpenRA.Mods.Cnc/UtilityCommands/ImportRedAlertMapCommand.cs
@@ -16,14 +16,13 @@ using System.Linq;
 using System.Text;
 using OpenRA.Mods.Cnc.FileFormats;
 using OpenRA.Mods.Common.FileFormats;
-using OpenRA.Mods.Common.UtilityCommands;
 
 namespace OpenRA.Mods.Cnc.UtilityCommands
 {
-	class ImportRedAlertLegacyMapCommand : ImportLegacyMapCommand, IUtilityCommand
+	class ImportRedAlertMapCommand : ImportGen1MapCommand, IUtilityCommand
 	{
 		// TODO: 128x128 is probably not true for "mega maps" from the expansions.
-		public ImportRedAlertLegacyMapCommand()
+		public ImportRedAlertMapCommand()
 			: base(128) { }
 
 		string IUtilityCommand.Name => "--import-ra-map";
diff --git a/OpenRA.Mods.Cnc/UtilityCommands/ImportTiberianDawnLegacyMapCommand.cs b/OpenRA.Mods.Cnc/UtilityCommands/ImportTiberianDawnMapCommand.cs
similarity index 96%
rename from OpenRA.Mods.Cnc/UtilityCommands/ImportTiberianDawnLegacyMapCommand.cs
rename to OpenRA.Mods.Cnc/UtilityCommands/ImportTiberianDawnMapCommand.cs
index 29f8238d3c..84cd1ddfb6 100644
--- a/OpenRA.Mods.Cnc/UtilityCommands/ImportTiberianDawnLegacyMapCommand.cs
+++ b/OpenRA.Mods.Cnc/UtilityCommands/ImportTiberianDawnMapCommand.cs
@@ -14,14 +14,13 @@ using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using OpenRA.Mods.Common.FileFormats;
-using OpenRA.Mods.Common.UtilityCommands;
 
 namespace OpenRA.Mods.Cnc.UtilityCommands
 {
-	class ImportTiberianDawnLegacyMapCommand : ImportLegacyMapCommand, IUtilityCommand
+	class ImportTiberianDawnMapCommand : ImportGen1MapCommand, IUtilityCommand
 	{
 		// NOTE: 64x64 map size is a C&C95 engine limitation
-		public ImportTiberianDawnLegacyMapCommand()
+		public ImportTiberianDawnMapCommand()
 			: base(64) { }
 
 		string IUtilityCommand.Name => "--import-td-map";
diff --git a/OpenRA.Mods.Common/UtilityCommands/Extensions.cs b/OpenRA.Mods.Common/UtilityCommands/Extensions.cs
deleted file mode 100644
index 73470b6d12..0000000000
--- a/OpenRA.Mods.Common/UtilityCommands/Extensions.cs
+++ /dev/null
@@ -1,29 +0,0 @@
-#region Copyright & License Information
-/*
- * Copyright (c) The OpenRA Developers and Contributors
- * 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, either version 3 of
- * the License, or (at your option) any later version. For more
- * information, see COPYING.
- */
-#endregion
-
-using System;
-using System.Collections.Generic;
-
-namespace OpenRA.Mods.Common.UtilityCommands
-{
-	public static class Extensions
-	{
-		public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
-		{
-			var knownKeys = new HashSet<TKey>();
-			foreach (var element in source)
-			{
-				if (knownKeys.Add(keySelector(element)))
-					yield return element;
-			}
-		}
-	}
-}