diff --git a/OpenRA.Game/Primitives/SpatiallyPartitioned.cs b/OpenRA.Game/Primitives/SpatiallyPartitioned.cs
index 6bc9833300..128832fe4d 100644
--- a/OpenRA.Game/Primitives/SpatiallyPartitioned.cs
+++ b/OpenRA.Game/Primitives/SpatiallyPartitioned.cs
@@ -30,14 +30,22 @@ namespace OpenRA.Primitives
 			itemBoundsBins = Exts.MakeArray(rows * cols, _ => new Dictionary<T, Rectangle>());
 		}
 
+		void ValidateBounds(Rectangle bounds)
+		{
+			if (bounds.Width <= 0 || bounds.Height <= 0)
+				throw new ArgumentException("bounds must be non-empty.", "bounds");
+		}
+
 		public void Add(T item, Rectangle bounds)
 		{
+			ValidateBounds(bounds);
 			itemBounds.Add(item, bounds);
 			MutateBins(item, bounds, addItem);
 		}
 
 		public void Update(T item, Rectangle bounds)
 		{
+			ValidateBounds(bounds);
 			MutateBins(item, itemBounds[item], removeItem);
 			MutateBins(item, itemBounds[item] = bounds, addItem);
 		}
diff --git a/OpenRA.Mods.Common/Traits/Immobile.cs b/OpenRA.Mods.Common/Traits/Immobile.cs
index be0ea75bbd..2926c02e25 100644
--- a/OpenRA.Mods.Common/Traits/Immobile.cs
+++ b/OpenRA.Mods.Common/Traits/Immobile.cs
@@ -55,14 +55,18 @@ namespace OpenRA.Mods.Common.Traits
 		{
 			self.World.ActorMap.AddInfluence(self, this);
 			self.World.ActorMap.AddPosition(self, this);
-			self.World.ScreenMap.Add(self);
+
+			if (!self.Bounds.Size.IsEmpty)
+				self.World.ScreenMap.Add(self);
 		}
 
 		public void RemovedFromWorld(Actor self)
 		{
 			self.World.ActorMap.RemoveInfluence(self, this);
 			self.World.ActorMap.RemovePosition(self, this);
-			self.World.ScreenMap.Remove(self);
+
+			if (!self.Bounds.Size.IsEmpty)
+				self.World.ScreenMap.Remove(self);
 		}
 	}
 }