diff --git a/OpenRA.Game/Network/Session.cs b/OpenRA.Game/Network/Session.cs
index bf9ad08ea2..25af7dcaa1 100644
--- a/OpenRA.Game/Network/Session.cs
+++ b/OpenRA.Game/Network/Session.cs
@@ -68,7 +68,7 @@ namespace OpenRA.Network
 			public string[] Mods = { "ra" };	// mod names
 			public int OrderLatency = 3;
 			public int RandomSeed = 0;
-			public bool LockTeams = false;	// don't allow team changes after game start.
+			public bool LockTeams = true;	// don't allow team changes after game start.
 			public bool AllowCheats = false;
 		}