diff --git a/OpenRA.Mods.Common/AI/AIHarvesterManager.cs b/OpenRA.Mods.Common/AI/AIHarvesterManager.cs
index 51b1701fe6..33f636af29 100644
--- a/OpenRA.Mods.Common/AI/AIHarvesterManager.cs
+++ b/OpenRA.Mods.Common/AI/AIHarvesterManager.cs
@@ -61,18 +61,15 @@ namespace OpenRA.Mods.Common.AI
 			return path[0];
 		}
 
-		public void Tick(List<Actor> activeUnits)
+		public void Tick(List<Actor> harvesters)
 		{
 			if (resLayer == null || resLayer.IsResourceLayerEmpty)
 				return;
 
 			// Find idle harvesters and give them orders:
-			foreach (var harvester in activeUnits)
+			foreach (var harvester in harvesters)
 			{
-				var harv = harvester.TraitOrDefault<Harvester>();
-				if (harv == null)
-					continue;
-
+				var harv = harvester.Trait<Harvester>();
 				if (!harv.IsEmpty)
 					continue;
 
diff --git a/OpenRA.Mods.Common/AI/HackyAI.cs b/OpenRA.Mods.Common/AI/HackyAI.cs
index 5227c30a33..cb88344b72 100644
--- a/OpenRA.Mods.Common/AI/HackyAI.cs
+++ b/OpenRA.Mods.Common/AI/HackyAI.cs
@@ -286,6 +286,10 @@ namespace OpenRA.Mods.Common.AI
 		// Units that the ai already knows about. Any unit not on this list needs to be given a role.
 		List<Actor> activeUnits = new List<Actor>();
 
+		// Harvesters are usually listed under ExcludeFromSquads, so they're not included in the activeUnits list, but still needed in AIHarvesterManager.
+		// TODO: Consider adding an explicit UnitsCommonNames.Harvester category.
+		List<Actor> harvesters = new List<Actor>();
+
 		public const int FeedbackTime = 30; // ticks; = a bit over 1s. must be >= netlag.
 
 		public readonly World World;
@@ -597,6 +601,7 @@ namespace OpenRA.Mods.Common.AI
 
 			activeUnits.RemoveAll(unitCannotBeOrdered);
 			unitsHangingAroundTheBase.RemoveAll(unitCannotBeOrdered);
+			harvesters.RemoveAll(unitCannotBeOrdered);
 
 			if (--rushTicks <= 0)
 			{
@@ -615,7 +620,7 @@ namespace OpenRA.Mods.Common.AI
 			{
 				assignRolesTicks = Info.AssignRolesInterval;
 				FindNewUnits(self);
-				harvManager.Tick(activeUnits);
+				harvManager.Tick(harvesters);
 				InitializeBase(self, true);
 			}
 
@@ -738,10 +743,13 @@ namespace OpenRA.Mods.Common.AI
 		void FindNewUnits(Actor self)
 		{
 			var newUnits = self.World.ActorsHavingTrait<IPositionable>()
-				.Where(a => a.Owner == Player && !activeUnits.Contains(a));
+				.Where(a => a.Owner == Player && !activeUnits.Contains(a) && !harvesters.Contains(a));
 
 			foreach (var a in newUnits)
 			{
+				if (a.Info.HasTraitInfo<HarvesterInfo>())
+					harvesters.Add(a);
+
 				if (Info.UnitsCommonNames.Mcv.Contains(a.Info.Name) || Info.UnitsCommonNames.ExcludeFromSquads.Contains(a.Info.Name))
 					continue;