diff --git a/OpenRA.Mods.Common/UpdateRules/Rules/20201213/RenameMPTraits.cs b/OpenRA.Mods.Common/UpdateRules/Rules/20201213/RenameMPTraits.cs
new file mode 100644
index 0000000000..3f1d83e0c9
--- /dev/null
+++ b/OpenRA.Mods.Common/UpdateRules/Rules/20201213/RenameMPTraits.cs
@@ -0,0 +1,38 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2020 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, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.Collections.Generic;
+
+namespace OpenRA.Mods.Common.UpdateRules.Rules
+{
+	public class RenameMPTraits : UpdateRule
+	{
+		public override string Name { get { return "Several traits spawning map actors and players have been renamed."; } }
+
+		public override string Description
+		{
+			get
+			{
+				return "'SpawnMPUnits' was renamed to 'SpawnStartingUnits', 'MPStartUnits' to 'StartingUnits', 'MPStartLocations' to " +
+					"'MapStartingLocations', and 'CreateMPPlayers' to 'CreateMapPlayers'.";
+			}
+		}
+
+		public override IEnumerable<string> UpdateActorNode(ModData modData, MiniYamlNode actorNode)
+		{
+			actorNode.RenameChildrenMatching("SpawnMPUnits", "SpawnStartingUnits");
+			actorNode.RenameChildrenMatching("MPStartUnits", "StartingUnits");
+			actorNode.RenameChildrenMatching("MPStartLocations", "MapStartingLocations");
+			actorNode.RenameChildrenMatching("CreateMPPlayers", "CreateMapPlayers");
+			yield break;
+		}
+	}
+}
diff --git a/OpenRA.Mods.Common/UpdateRules/UpdatePath.cs b/OpenRA.Mods.Common/UpdateRules/UpdatePath.cs
index c58cb3f278..201bc94b84 100644
--- a/OpenRA.Mods.Common/UpdateRules/UpdatePath.cs
+++ b/OpenRA.Mods.Common/UpdateRules/UpdatePath.cs
@@ -53,9 +53,9 @@ namespace OpenRA.Mods.Common.UpdateRules
 				new RenameRallyPointPath(),
 			}),
 
-			new UpdatePath("release-20200503", new UpdateRule[]
+			new UpdatePath("release-20200503", "playtest-20201213", new UpdateRule[]
 			{
-				// Bleed only changes here
+				// Prep only changes here
 				new AddPipDecorationTraits(),
 				new ModernizeDecorationTraits(),
 				new RenameHealCrateAction(),
@@ -79,6 +79,12 @@ namespace OpenRA.Mods.Common.UpdateRules
 				new RenameCircleContrast(),
 				new SplitDamagedByTerrain(),
 				new RemoveLaysTerrain(),
+			}),
+
+			new UpdatePath("playtest-20201213", new UpdateRule[]
+			{
+				// Bleed only changes here
+				new RenameMPTraits(),
 			})
 		};