diff --git a/OpenRA.Mods.Common/Pathfinder/PathSearch.cs b/OpenRA.Mods.Common/Pathfinder/PathSearch.cs
index e127192856..9a57aa007c 100644
--- a/OpenRA.Mods.Common/Pathfinder/PathSearch.cs
+++ b/OpenRA.Mods.Common/Pathfinder/PathSearch.cs
@@ -48,7 +48,7 @@ namespace OpenRA.Mods.Common.Pathfinder
 
 			foreach (var sl in froms)
 				if (world.Map.Contains(sl))
-					search.AddInitialCell(sl);
+					search.AddInitialCell(sl, customCost);
 
 			return search;
 		}
@@ -75,7 +75,7 @@ namespace OpenRA.Mods.Common.Pathfinder
 
 			foreach (var sl in froms)
 				if (world.Map.Contains(sl))
-					search.AddInitialCell(sl);
+					search.AddInitialCell(sl, customCost);
 
 			return search;
 		}
@@ -87,7 +87,7 @@ namespace OpenRA.Mods.Common.Pathfinder
 			var graph = new SparsePathGraph(edges, estimatedSearchSize);
 			var search = new PathSearch(graph, DefaultCostEstimator(locomotor, target), 100, loc => loc == target, recorder);
 
-			search.AddInitialCell(from);
+			search.AddInitialCell(from, null);
 
 			return search;
 		}
@@ -162,10 +162,18 @@ namespace OpenRA.Mods.Common.Pathfinder
 			openQueue = new PriorityQueue<GraphConnection>(GraphConnection.ConnectionCostComparer);
 		}
 
-		void AddInitialCell(CPos location)
+		void AddInitialCell(CPos location, Func<CPos, int> customCost)
 		{
+			var initialCost = 0;
+			if (customCost != null)
+			{
+				initialCost = customCost(location);
+				if (initialCost == PathGraph.PathCostForInvalidPath)
+					return;
+			}
+
 			var estimatedCost = heuristic(location) * heuristicWeightPercentage / 100;
-			Graph[location] = new CellInfo(CellStatus.Open, 0, estimatedCost, location);
+			Graph[location] = new CellInfo(CellStatus.Open, initialCost, initialCost + estimatedCost, location);
 			var connection = new GraphConnection(location, estimatedCost);
 			openQueue.Add(connection);
 		}
diff --git a/OpenRA.Mods.Common/Traits/Harvester.cs b/OpenRA.Mods.Common/Traits/Harvester.cs
index 163421cc52..3fbe209927 100644
--- a/OpenRA.Mods.Common/Traits/Harvester.cs
+++ b/OpenRA.Mods.Common/Traits/Harvester.cs
@@ -15,7 +15,6 @@ using System.Collections.ObjectModel;
 using System.Linq;
 using OpenRA.Mods.Common.Activities;
 using OpenRA.Mods.Common.Orders;
-using OpenRA.Mods.Common.Pathfinder;
 using OpenRA.Primitives;
 using OpenRA.Traits;
 
@@ -183,6 +182,7 @@ namespace OpenRA.Mods.Common.Traits
 		public Actor ClosestProc(Actor self, Actor ignore)
 		{
 			// Find all refineries and their occupancy count:
+			// Exclude refineries with too many harvesters clogging the delivery location.
 			var refineries = self.World.ActorsWithTrait<IAcceptResources>()
 				.Where(r => r.Actor != ignore && r.Actor.Owner == self.Owner && IsAcceptableProcType(r.Actor))
 				.Select(r => new
@@ -190,28 +190,28 @@ namespace OpenRA.Mods.Common.Traits
 					Location = r.Actor.Location + r.Trait.DeliveryOffset,
 					Actor = r.Actor,
 					Occupancy = self.World.ActorsHavingTrait<Harvester>(h => h.LinkedProc == r.Actor).Count()
-				}).ToLookup(r => r.Location);
+				})
+				.Where(r => r.Occupancy < Info.MaxUnloadQueue)
+				.ToDictionary(r => r.Location);
+
+			if (refineries.Count == 0)
+				return null;
 
 			// Start a search from each refinery's delivery location:
 			var path = mobile.PathFinder.FindPathToTargetCell(
 				self, refineries.Select(r => r.Key), self.Location, BlockedByActor.None,
 				location =>
 				{
-					if (!refineries.Contains(location))
+					if (!refineries.ContainsKey(location))
 						return 0;
 
-					var occupancy = refineries[location].First().Occupancy;
-
-					// Too many harvesters clogs up the refinery's delivery location:
-					if (occupancy >= Info.MaxUnloadQueue)
-						return PathGraph.PathCostForInvalidPath;
-
 					// Prefer refineries with less occupancy (multiplier is to offset distance cost):
+					var occupancy = refineries[location].Occupancy;
 					return occupancy * Info.UnloadQueueCostModifier;
 				});
 
 			if (path.Count > 0)
-				return refineries[path.Last()].First().Actor;
+				return refineries[path.Last()].Actor;
 
 			return null;
 		}
diff --git a/OpenRA.Mods.Common/Traits/World/PathFinder.cs b/OpenRA.Mods.Common/Traits/World/PathFinder.cs
index 7a699fb0ec..d3e18ba674 100644
--- a/OpenRA.Mods.Common/Traits/World/PathFinder.cs
+++ b/OpenRA.Mods.Common/Traits/World/PathFinder.cs
@@ -102,7 +102,9 @@ namespace OpenRA.Mods.Common.Traits
 				// For adjacent cells on the same layer, we can return the path without invoking a full search.
 				if (source.Layer == target.Layer && (source - target).LengthSquared < 3)
 				{
-					if (!world.Map.Contains(source))
+					// If the source cell is inaccessible, there is no path.
+					if (!world.Map.Contains(source) ||
+						(customCost != null && customCost(source) == PathGraph.PathCostForInvalidPath))
 						return NoPath;
 					return new List<CPos>(2) { target, source };
 				}