diff --git a/OpenRA.Game/Map.cs b/OpenRA.Game/Map.cs
index d44a0a89cf..391a896a7a 100644
--- a/OpenRA.Game/Map.cs
+++ b/OpenRA.Game/Map.cs
@@ -417,9 +417,12 @@ namespace OpenRA
 		}
 
 		public void Resize(int width, int height)		// editor magic.
-		{
-			MapTiles = Lazy.New(() => ResizeArray(MapTiles.Value, MapTiles.Value[0, 0], width, height));
-			MapResources = Lazy.New(() => ResizeArray(MapResources.Value, MapResources.Value[0, 0], width, height));
+		{
+			var oldMapTiles = MapTiles.Value;
+			var oldMapResources = MapResources.Value;
+
+			MapTiles = Lazy.New(() => ResizeArray(oldMapTiles, oldMapTiles[0, 0], width, height));
+			MapResources = Lazy.New(() => ResizeArray(oldMapResources, oldMapResources[0, 0], width, height));
 			MapSize = new int2(width, height);
 		}