diff --git a/OpenRA.Mods.Common/Traits/World/SmudgeLayer.cs b/OpenRA.Mods.Common/Traits/World/SmudgeLayer.cs
index 2d42270d0d..f12873d3a0 100644
--- a/OpenRA.Mods.Common/Traits/World/SmudgeLayer.cs
+++ b/OpenRA.Mods.Common/Traits/World/SmudgeLayer.cs
@@ -151,7 +151,7 @@ namespace OpenRA.Mods.Common.Traits
 			else
 			{
 				// Existing smudge; make it deeper
-				var tile = dirty.ContainsKey(loc) ? dirty[loc] : tiles[loc];
+				var tile = dirty.ContainsKey(loc) && dirty[loc].Sprite != null ? dirty[loc] : tiles[loc];
 				var maxDepth = smudges[tile.Type].Length;
 				if (tile.Depth < maxDepth - 1)
 				{