diff --git a/OpenRa.Game/UnitInfluenceMap.cs b/OpenRa.Game/UnitInfluenceMap.cs
index 29bc3f6255..64fa602104 100644
--- a/OpenRa.Game/UnitInfluenceMap.cs
+++ b/OpenRa.Game/UnitInfluenceMap.cs
@@ -2,27 +2,47 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
+using OpenRa.Game.Traits;
 
 namespace OpenRa.Game
 {
 	class UnitInfluenceMap
 	{
 		Actor[,] influence = new Actor[128, 128];
-
-		/* todo: incremental updates for great justice [and perf] */
+		readonly int2 searchDistance = new int2(1, 1);
 
 		public void Tick()
 		{
-			influence = new Actor[128, 128];
-
 			var units = Game.world.Actors
 				.Select( a => a.traits.GetOrDefault<Traits.Mobile>() ).Where( m => m != null );
 
 			foreach (var u in units)
-				foreach (var c in u.OccupiedCells())
-					influence[c.X, c.Y] = u.self;
+				Update(u);
 		}
 
 		public Actor GetUnitAt(int2 a) { return influence[a.X, a.Y]; }
+
+		public void Add(Mobile a)
+		{
+			foreach (var c in a.OccupiedCells())
+				influence[c.X, c.Y] = a.self;
+		}
+
+		public void Remove(Mobile a)
+		{
+			var min = int2.Max(new int2(0, 0), a.self.Location - searchDistance);
+			var max = int2.Min(new int2(128, 128), a.self.Location + searchDistance);
+
+			for (var j = min.Y; j <= max.Y; j++)
+				for (var i = min.X; i <= max.X; i++)
+					if (influence[i, j] == a.self)
+						influence[i, j] = null;
+		}
+
+		public void Update(Mobile a)
+		{
+			Remove(a);
+			if (!a.self.IsDead) Add(a);
+		}
 	}
 }