diff --git a/OpenRA.Game/Network/Session.cs b/OpenRA.Game/Network/Session.cs
index c2e995b140..c10ff6fe82 100644
--- a/OpenRA.Game/Network/Session.cs
+++ b/OpenRA.Game/Network/Session.cs
@@ -82,7 +82,7 @@ namespace OpenRA.Network
 			public string[] Mods = { "ra" };	// mod names
 			public int OrderLatency = 3;
 			public int RandomSeed = 0;
-			public bool LockTeams = true;	// don't allow team changes after game start.
+			public bool FragileAlliances = false;	// Allow diplomatic stance changes after game start.
 			public bool AllowCheats = false;
 			public bool Dedicated;
 			public string Difficulty;
diff --git a/OpenRA.Game/Network/UnitOrders.cs b/OpenRA.Game/Network/UnitOrders.cs
index e1db2476f1..a1259da378 100755
--- a/OpenRA.Game/Network/UnitOrders.cs
+++ b/OpenRA.Game/Network/UnitOrders.cs
@@ -163,7 +163,7 @@ namespace OpenRA.Network
 
 				case "SetStance":
 					{
-						if (Game.orderManager.LobbyInfo.GlobalSettings.LockTeams)
+						if (!Game.orderManager.LobbyInfo.GlobalSettings.FragileAlliances)
 							return;
 
 						var targetPlayer = order.Player.World.Players.FirstOrDefault(p => p.InternalName == order.TargetString);
diff --git a/OpenRA.Game/Widgets/CheckboxWidget.cs b/OpenRA.Game/Widgets/CheckboxWidget.cs
index a896c70f62..e2378a2a7d 100644
--- a/OpenRA.Game/Widgets/CheckboxWidget.cs
+++ b/OpenRA.Game/Widgets/CheckboxWidget.cs
@@ -56,7 +56,8 @@ namespace OpenRA.Widgets
 
 			var textSize = font.Measure(Text);
 			font.DrawText(Text,
-				new float2(rect.Left + rect.Height * 1.5f, RenderOrigin.Y - BaseLine + (Bounds.Height - textSize.Y)/2), Color.White);
+				new float2(rect.Left + rect.Height * 1.5f, RenderOrigin.Y - BaseLine + (Bounds.Height - textSize.Y)/2),
+				disabled ? Color.Gray : Color.White);
 
 			if (IsChecked() || (Depressed && HasPressedState && !disabled))
 			{
diff --git a/OpenRA.Mods.RA/ServerTraits/LobbyCommands.cs b/OpenRA.Mods.RA/ServerTraits/LobbyCommands.cs
index cfbf1b086b..11dcbe635a 100644
--- a/OpenRA.Mods.RA/ServerTraits/LobbyCommands.cs
+++ b/OpenRA.Mods.RA/ServerTraits/LobbyCommands.cs
@@ -292,7 +292,7 @@ namespace OpenRA.Mods.RA.Server
 						server.SyncLobbyInfo();
 						return true;
 					}},
-				{ "lockteams",
+				{ "fragilealliance",
 					s =>
 					{
 						if (!client.IsAdmin)
@@ -301,7 +301,7 @@ namespace OpenRA.Mods.RA.Server
 							return true;
 						}
 
-						bool.TryParse(s, out server.lobbyInfo.GlobalSettings.LockTeams);
+						bool.TryParse(s, out server.lobbyInfo.GlobalSettings.FragileAlliances);
 						server.SyncLobbyInfo();
 						return true;
 					}},
diff --git a/OpenRA.Mods.RA/Widgets/Logic/DiplomacyLogic.cs b/OpenRA.Mods.RA/Widgets/Logic/DiplomacyLogic.cs
index 7673691c24..b2e6b46ed0 100644
--- a/OpenRA.Mods.RA/Widgets/Logic/DiplomacyLogic.cs
+++ b/OpenRA.Mods.RA/Widgets/Logic/DiplomacyLogic.cs
@@ -111,6 +111,9 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 					GetText = () => world.LocalPlayer.Stances[ pp ].ToString(),
 				};
 
+				if (!p.World.LobbyInfo.GlobalSettings.FragileAlliances)
+					myStance.Disabled = true;
+
 				myStance.OnMouseDown = mi => ShowDropDown(pp, myStance);
 
 				bg.AddChild(myStance);
@@ -138,7 +141,7 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 
 		void SetStance(ButtonWidget bw, Player p, Stance ss)
 		{
-			if (p.World.LobbyInfo.GlobalSettings.LockTeams)
+			if (!p.World.LobbyInfo.GlobalSettings.FragileAlliances)
 				return;	// team changes are banned
 
 			// NOTE(jsd): Abuse of the type system here with `CPos`
diff --git a/OpenRA.Mods.RA/Widgets/Logic/LobbyLogic.cs b/OpenRA.Mods.RA/Widgets/Logic/LobbyLogic.cs
index 9f2aaf3acc..aa8548b4f0 100644
--- a/OpenRA.Mods.RA/Widgets/Logic/LobbyLogic.cs
+++ b/OpenRA.Mods.RA/Widgets/Logic/LobbyLogic.cs
@@ -36,6 +36,8 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 		readonly Action onExit;
 		readonly OrderManager orderManager;
 
+		public bool TeamGame;
+
 		// Listen for connection failures
 		void ConnectionStateChanged(OrderManager om)
 		{
@@ -204,6 +206,17 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 					"crates {0}".F(!orderManager.LobbyInfo.GlobalSettings.Crates)));
 			}
 
+			var fragileAlliance = lobby.GetOrNull<CheckboxWidget>("FRAGILEALLIANCES_CHECKBOX");
+			if (fragileAlliance != null)
+			{
+				fragileAlliance.IsChecked = () => orderManager.LobbyInfo.GlobalSettings.FragileAlliances;
+				fragileAlliance.IsDisabled = () => !Game.IsHost || gameStarting || orderManager.LocalClient == null
+					|| orderManager.LocalClient.IsReady || TeamGame; // only available in FFA
+				fragileAlliance.OnClick = () => orderManager.IssueOrder(Order.Command(
+					"fragilealliance {0}".F(!orderManager.LobbyInfo.GlobalSettings.FragileAlliances)));
+			};
+
+
 			var difficulty = lobby.GetOrNull<DropDownButtonWidget>("DIFFICULTY_DROPDOWNBUTTON");
 			if (difficulty != null)
 			{
@@ -326,6 +339,8 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 		void UpdatePlayerList()
 		{
 			var idx = 0;
+			TeamGame = false;
+
 			foreach (var kv in orderManager.LobbyInfo.Slots)
 			{
 				var key = kv.Key;
@@ -414,6 +429,9 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 					team.OnMouseDown = _ => LobbyUtils.ShowTeamDropDown(team, client, orderManager, Map);
 					team.GetText = () => (client.Team == 0) ? "-" : client.Team.ToString();
 
+					if (slot.LockTeam || client.Team > 0)
+						TeamGame = true;
+
 					if (client.Bot == null)
 					{
 						// local player
@@ -552,6 +570,9 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 
 			while (Players.Children.Count > idx)
 				Players.RemoveChild(Players.Children[idx]);
+
+			if (orderManager.LobbyInfo.GlobalSettings.FragileAlliances && TeamGame)
+				orderManager.IssueOrder(Order.Command("fragilealliance false")); // No back-stabbing in Team games.
 		}
 
 		void CycleReady()
diff --git a/mods/ra/chrome/lobby.yaml b/mods/ra/chrome/lobby.yaml
index 410f1b59ff..e260d375d3 100644
--- a/mods/ra/chrome/lobby.yaml
+++ b/mods/ra/chrome/lobby.yaml
@@ -420,9 +420,15 @@ Background@SERVER_LOBBY:
 			Width: 80
 			Height: 20
 			Text: Crates
+		Checkbox@FRAGILEALLIANCES_CHECKBOX:
+			X: PARENT_RIGHT-154
+			Y: PARENT_BOTTOM-119
+			Width: 80
+			Height: 20
+			Text: Fragile Alliances
 		Button@DISCONNECT_BUTTON:
 			X:PARENT_RIGHT-154
-			Y:PARENT_BOTTOM-99
+			Y:PARENT_BOTTOM-94
 			Width:120
 			Height:25
 			Text:Disconnect