diff --git a/OpenRA.Mods.Common/Scripting/ScriptTriggers.cs b/OpenRA.Mods.Common/Scripting/ScriptTriggers.cs
index 502ed8ad1b..7c69e79285 100644
--- a/OpenRA.Mods.Common/Scripting/ScriptTriggers.cs
+++ b/OpenRA.Mods.Common/Scripting/ScriptTriggers.cs
@@ -175,7 +175,7 @@ namespace OpenRA.Mods.Common.Scripting
 			OnProducedInternal(self, other);
 		}
 
-		public void OnPlayerWon(Player player)
+		void INotifyObjectivesUpdated.OnPlayerWon(Player player)
 		{
 			if (world.Disposing)
 				return;
@@ -195,7 +195,7 @@ namespace OpenRA.Mods.Common.Scripting
 			}
 		}
 
-		public void OnPlayerLost(Player player)
+		void INotifyObjectivesUpdated.OnPlayerLost(Player player)
 		{
 			if (world.Disposing)
 				return;
@@ -215,7 +215,7 @@ namespace OpenRA.Mods.Common.Scripting
 			}
 		}
 
-		public void OnObjectiveAdded(Player player, int id)
+		void INotifyObjectivesUpdated.OnObjectiveAdded(Player player, int id)
 		{
 			if (world.Disposing)
 				return;
@@ -236,7 +236,7 @@ namespace OpenRA.Mods.Common.Scripting
 			}
 		}
 
-		public void OnObjectiveCompleted(Player player, int id)
+		void INotifyObjectivesUpdated.OnObjectiveCompleted(Player player, int id)
 		{
 			if (world.Disposing)
 				return;
@@ -257,7 +257,7 @@ namespace OpenRA.Mods.Common.Scripting
 			}
 		}
 
-		public void OnObjectiveFailed(Player player, int id)
+		void INotifyObjectivesUpdated.OnObjectiveFailed(Player player, int id)
 		{
 			if (world.Disposing)
 				return;
diff --git a/OpenRA.Mods.Common/Traits/Player/ConquestVictoryConditions.cs b/OpenRA.Mods.Common/Traits/Player/ConquestVictoryConditions.cs
index d8b37e51b4..a4616313c0 100644
--- a/OpenRA.Mods.Common/Traits/Player/ConquestVictoryConditions.cs
+++ b/OpenRA.Mods.Common/Traits/Player/ConquestVictoryConditions.cs
@@ -68,7 +68,7 @@ namespace OpenRA.Mods.Common.Traits
 			mo.MarkCompleted(self.Owner, objectiveID);
 		}
 
-		public void OnPlayerLost(Player player)
+		void INotifyObjectivesUpdated.OnPlayerLost(Player player)
 		{
 			foreach (var a in player.World.ActorsWithTrait<INotifyOwnerLost>().Where(a => a.Actor.Owner == player))
 				a.Trait.OnOwnerLost(a.Actor);
@@ -84,7 +84,7 @@ namespace OpenRA.Mods.Common.Traits
 			});
 		}
 
-		public void OnPlayerWon(Player player)
+		void INotifyObjectivesUpdated.OnPlayerWon(Player player)
 		{
 			if (info.SuppressNotifications)
 				return;
@@ -97,8 +97,8 @@ namespace OpenRA.Mods.Common.Traits
 			});
 		}
 
-		public void OnObjectiveAdded(Player player, int id) { }
-		public void OnObjectiveCompleted(Player player, int id) { }
-		public void OnObjectiveFailed(Player player, int id) { }
+		void INotifyObjectivesUpdated.OnObjectiveAdded(Player player, int id) { }
+		void INotifyObjectivesUpdated.OnObjectiveCompleted(Player player, int id) { }
+		void INotifyObjectivesUpdated.OnObjectiveFailed(Player player, int id) { }
 	}
 }
diff --git a/OpenRA.Mods.Common/Traits/Player/MissionObjectives.cs b/OpenRA.Mods.Common/Traits/Player/MissionObjectives.cs
index 47001d48a7..1faf5bf158 100644
--- a/OpenRA.Mods.Common/Traits/Player/MissionObjectives.cs
+++ b/OpenRA.Mods.Common/Traits/Player/MissionObjectives.cs
@@ -168,7 +168,7 @@ namespace OpenRA.Mods.Common.Traits
 				});
 		}
 
-		public void OnPlayerWon(Player player)
+		void INotifyObjectivesUpdated.OnPlayerWon(Player player)
 		{
 			var players = player.World.Players.Where(p => !p.NonCombatant);
 			var enemies = players.Where(p => !p.IsAlliedWith(player));
@@ -204,7 +204,7 @@ namespace OpenRA.Mods.Common.Traits
 			CheckIfGameIsOver(player);
 		}
 
-		public void OnPlayerLost(Player player)
+		void INotifyObjectivesUpdated.OnPlayerLost(Player player)
 		{
 			var players = player.World.Players.Where(p => !p.NonCombatant);
 			var enemies = players.Where(p => !p.IsAlliedWith(player));
@@ -259,9 +259,9 @@ namespace OpenRA.Mods.Common.Traits
 
 		public event Action<Player, bool> ObjectiveAdded = (player, inhibitAnnouncement) => { player.HasObjectives = true; };
 
-		public void OnObjectiveAdded(Player player, int id) { }
-		public void OnObjectiveCompleted(Player player, int id) { }
-		public void OnObjectiveFailed(Player player, int id) { }
+		void INotifyObjectivesUpdated.OnObjectiveAdded(Player player, int id) { }
+		void INotifyObjectivesUpdated.OnObjectiveCompleted(Player player, int id) { }
+		void INotifyObjectivesUpdated.OnObjectiveFailed(Player player, int id) { }
 
 		public void ResolveOrder(Actor self, Order order)
 		{
diff --git a/OpenRA.Mods.Common/Traits/Player/StrategicVictoryConditions.cs b/OpenRA.Mods.Common/Traits/Player/StrategicVictoryConditions.cs
index 26306009b6..1755b3b680 100644
--- a/OpenRA.Mods.Common/Traits/Player/StrategicVictoryConditions.cs
+++ b/OpenRA.Mods.Common/Traits/Player/StrategicVictoryConditions.cs
@@ -107,7 +107,7 @@ namespace OpenRA.Mods.Common.Traits
 			}
 		}
 
-		public void OnPlayerLost(Player player)
+		void INotifyObjectivesUpdated.OnPlayerLost(Player player)
 		{
 			foreach (var a in player.World.ActorsWithTrait<INotifyOwnerLost>().Where(a => a.Actor.Owner == player))
 				a.Trait.OnOwnerLost(a.Actor);
@@ -123,7 +123,7 @@ namespace OpenRA.Mods.Common.Traits
 			});
 		}
 
-		public void OnPlayerWon(Player player)
+		void INotifyObjectivesUpdated.OnPlayerWon(Player player)
 		{
 			if (info.SuppressNotifications)
 				return;
@@ -136,8 +136,8 @@ namespace OpenRA.Mods.Common.Traits
 			});
 		}
 
-		public void OnObjectiveAdded(Player player, int id) { }
-		public void OnObjectiveCompleted(Player player, int id) { }
-		public void OnObjectiveFailed(Player player, int id) { }
+		void INotifyObjectivesUpdated.OnObjectiveAdded(Player player, int id) { }
+		void INotifyObjectivesUpdated.OnObjectiveCompleted(Player player, int id) { }
+		void INotifyObjectivesUpdated.OnObjectiveFailed(Player player, int id) { }
 	}
 }
diff --git a/OpenRA.Mods.Common/TraitsInterfaces.cs b/OpenRA.Mods.Common/TraitsInterfaces.cs
index 1b6cb57de1..3b3152df64 100644
--- a/OpenRA.Mods.Common/TraitsInterfaces.cs
+++ b/OpenRA.Mods.Common/TraitsInterfaces.cs
@@ -425,6 +425,7 @@ namespace OpenRA.Mods.Common.Traits
 		int ExitDelay { get; }
 	}
 
+	[RequireExplicitImplementation]
 	public interface INotifyObjectivesUpdated
 	{
 		void OnPlayerWon(Player winner);