diff --git a/ClassicalSharp/Map/Formats/MapLvl.Importer.cs b/ClassicalSharp/Map/Formats/MapLvl.Importer.cs
index c0dccc026..26b5917ec 100644
--- a/ClassicalSharp/Map/Formats/MapLvl.Importer.cs
+++ b/ClassicalSharp/Map/Formats/MapLvl.Importer.cs
@@ -48,12 +48,14 @@ namespace ClassicalSharp.Map {
 		
 		void ReadCustomBlocks(Stream s, int width, int height, int length, byte[] blocks) {
 			byte[] chunk = new byte[16 * 16 * 16];
+			byte[] data = new byte[1];
 			
 			for (int y = 0; y < height; y += 16)
 				for (int z = 0; z < length; z += 16)
 					for (int x = 0; x < width; x += 16) 
 			{
-				if (s.ReadByte() != 1) continue;
+				int read = s.Read(data, 0, 1);
+				if (read == 0 || data[0] != 1) continue;
 				s.Read(chunk, 0, chunk.Length);
 				
 				int baseIndex = (y * length + z) * width + x;