diff --git a/OpenRA.Mods.Common/Terrain/DefaultTileCache.cs b/OpenRA.Mods.Common/Terrain/DefaultTileCache.cs
index 9f07456973..5d110ff498 100644
--- a/OpenRA.Mods.Common/Terrain/DefaultTileCache.cs
+++ b/OpenRA.Mods.Common/Terrain/DefaultTileCache.cs
@@ -36,22 +36,13 @@ namespace OpenRA.Mods.Common.Terrain
 	public sealed class DefaultTileCache : IDisposable
 	{
 		readonly Dictionary<ushort, TheaterTemplate> templates = new Dictionary<ushort, TheaterTemplate>();
-		SheetBuilder sheetBuilder;
+		readonly Cache<SheetType, SheetBuilder> sheetBuilders;
 		readonly Sprite missingTile;
 		readonly MersenneTwister random;
 
 		public DefaultTileCache(DefaultTerrain terrainInfo, Action<uint, string> onMissingImage = null)
 		{
-			var allocated = false;
-
-			Func<Sheet> allocate = () =>
-			{
-				if (allocated)
-					throw new SheetOverflowException("Terrain sheet overflow. Try increasing the tileset SheetSize parameter.");
-				allocated = true;
-
-				return new Sheet(SheetType.Indexed, new Size(terrainInfo.SheetSize, terrainInfo.SheetSize));
-			};
+			sheetBuilders = new Cache<SheetType, SheetBuilder>(t => new SheetBuilder(t, terrainInfo.SheetSize));
 
 			random = new MersenneTwister();
 
@@ -99,25 +90,16 @@ namespace OpenRA.Mods.Common.Terrain
 						var offset = new float3(f.Offset, zOffset);
 						var type = SheetBuilder.FrameTypeToSheetType(f.Type);
 
-						// Defer SheetBuilder creation until we know what type of frames we are loading!
-						// TODO: Support mixed indexed and BGRA frames
-						if (sheetBuilder == null)
-							sheetBuilder = new SheetBuilder(SheetBuilder.FrameTypeToSheetType(f.Type), allocate);
-						else if (type != sheetBuilder.Type)
-							throw new YamlException("Sprite type mismatch. Terrain sprites must all be either Indexed or RGBA.");
-
-						var s = sheetBuilder.Allocate(f.Size, zRamp, offset);
+						var s = sheetBuilders[type].Allocate(f.Size, zRamp, offset);
 						OpenRA.Graphics.Util.FastCopyIntoChannel(s, f.Data, f.Type);
 
 						if (terrainInfo.EnableDepth)
 						{
 							var depthFrame = allFrames[j + frameCount];
-							var ss = sheetBuilder.Allocate(f.Size, zRamp, offset);
+							var depthType = SheetBuilder.FrameTypeToSheetType(depthFrame.Type);
+							var ss = sheetBuilders[depthType].Allocate(depthFrame.Size, zRamp, offset);
 							OpenRA.Graphics.Util.FastCopyIntoChannel(ss, depthFrame.Data, depthFrame.Type);
-
-							// s and ss are guaranteed to use the same sheet
-							// because of the custom terrain sheet allocation
-							s = new SpriteWithSecondaryData(s, s.Sheet, ss.Bounds, ss.Channel);
+							s = new SpriteWithSecondaryData(s, ss.Sheet, ss.Bounds, ss.Channel);
 						}
 
 						return s;
@@ -137,12 +119,22 @@ namespace OpenRA.Mods.Common.Terrain
 			}
 
 			// 1x1px transparent tile
-			if (sheetBuilder.Type == SheetType.BGRA)
-				missingTile = sheetBuilder.Add(new byte[4], SpriteFrameType.Bgra32, new Size(1, 1));
-			else
-				missingTile = sheetBuilder.Add(new byte[1], SpriteFrameType.Indexed8, new Size(1, 1));
+			var missingDataLength = 1;
+			var missingFrameType = SpriteFrameType.Indexed8;
+			var missingSheetType = SheetType.Indexed;
 
-			Sheet.ReleaseBuffer();
+			// Avoid creating an indexed sheet if all tiles are BGRA
+			var missing = sheetBuilders.FirstOrDefault();
+			if (missing.Value != null && missing.Key == SheetType.BGRA)
+			{
+				missingDataLength = 4;
+				missingFrameType = SpriteFrameType.Bgra32;
+				missingSheetType = SheetType.BGRA;
+			}
+
+			missingTile = sheetBuilders[missingSheetType].Add(new byte[missingDataLength], missingFrameType, new Size(1, 1));
+			foreach (var sb in sheetBuilders.Values)
+				sb.Current.ReleaseBuffer();
 		}
 
 		public bool HasTileSprite(TerrainTile r, int? variant = null)
@@ -162,11 +154,12 @@ namespace OpenRA.Mods.Common.Terrain
 			return template.Sprites[start * template.Stride + r.Index];
 		}
 
-		public Sheet Sheet { get { return sheetBuilder.Current; } }
+		public Sprite MissingTile { get { return missingTile; } }
 
 		public void Dispose()
 		{
-			sheetBuilder.Dispose();
+			foreach (var sb in sheetBuilders.Values)
+				sb.Dispose();
 		}
 	}
 }
diff --git a/OpenRA.Mods.Common/Traits/World/TerrainRenderer.cs b/OpenRA.Mods.Common/Traits/World/TerrainRenderer.cs
index 5ee896e7ff..42d3cc2d33 100644
--- a/OpenRA.Mods.Common/Traits/World/TerrainRenderer.cs
+++ b/OpenRA.Mods.Common/Traits/World/TerrainRenderer.cs
@@ -80,9 +80,7 @@ namespace OpenRA.Mods.Common.Traits
 		void IWorldLoaded.WorldLoaded(World world, WorldRenderer wr)
 		{
 			worldRenderer = wr;
-			var emptySprite = new Sprite(tileCache.Sheet, Rectangle.Empty, TextureChannel.Alpha);
-			spriteLayer = new TerrainSpriteLayer(world, wr, emptySprite, BlendMode.Alpha, world.Type != WorldType.Editor);
-
+			spriteLayer = new TerrainSpriteLayer(world, wr, tileCache.MissingTile, BlendMode.Alpha, world.Type != WorldType.Editor);
 			foreach (var cell in map.AllCells)
 				UpdateCell(cell);
 
@@ -124,7 +122,7 @@ namespace OpenRA.Mods.Common.Traits
 			disposed = true;
 		}
 
-		Sheet ITiledTerrainRenderer.Sheet { get { return tileCache.Sheet; } }
+		Sprite ITiledTerrainRenderer.MissingTile { get { return tileCache.MissingTile; } }
 
 		Sprite ITiledTerrainRenderer.TileSprite(TerrainTile r, int? variant)
 		{
diff --git a/OpenRA.Mods.Common/TraitsInterfaces.cs b/OpenRA.Mods.Common/TraitsInterfaces.cs
index 51c483ffc1..7c6a11207e 100644
--- a/OpenRA.Mods.Common/TraitsInterfaces.cs
+++ b/OpenRA.Mods.Common/TraitsInterfaces.cs
@@ -654,7 +654,7 @@ namespace OpenRA.Mods.Common.Traits
 	[RequireExplicitImplementation]
 	public interface ITiledTerrainRenderer
 	{
-		Sheet Sheet { get; }
+		Sprite MissingTile { get; }
 		Sprite TileSprite(TerrainTile r, int? variant = null);
 		Rectangle TemplateBounds(TerrainTemplateInfo template);
 		IEnumerable<IRenderable> RenderUIPreview(WorldRenderer wr, TerrainTemplateInfo template, int2 origin, float scale);
diff --git a/OpenRA.Mods.D2k/Traits/World/BuildableTerrainLayer.cs b/OpenRA.Mods.D2k/Traits/World/BuildableTerrainLayer.cs
index a0f4133d2e..f790337f32 100644
--- a/OpenRA.Mods.D2k/Traits/World/BuildableTerrainLayer.cs
+++ b/OpenRA.Mods.D2k/Traits/World/BuildableTerrainLayer.cs
@@ -13,7 +13,6 @@ using System.Collections.Generic;
 using System.Linq;
 using OpenRA.Graphics;
 using OpenRA.Mods.Common.Traits;
-using OpenRA.Primitives;
 using OpenRA.Traits;
 
 namespace OpenRA.Mods.D2k.Traits
@@ -52,8 +51,7 @@ namespace OpenRA.Mods.D2k.Traits
 
 		void IWorldLoaded.WorldLoaded(World w, WorldRenderer wr)
 		{
-			var emptySprite = new Sprite(terrainRenderer.Sheet, Rectangle.Empty, TextureChannel.Alpha);
-			render = new TerrainSpriteLayer(w, wr, emptySprite, BlendMode.Alpha, wr.World.Type != WorldType.Editor);
+			render = new TerrainSpriteLayer(w, wr, terrainRenderer.MissingTile, BlendMode.Alpha, wr.World.Type != WorldType.Editor);
 			paletteReference = wr.Palette(info.Palette);
 		}