diff --git a/src/Client.Helpers.cs b/src/Client.Helpers.cs
index 9c7eafa..29c2eef 100644
--- a/src/Client.Helpers.cs
+++ b/src/Client.Helpers.cs
@@ -2,7 +2,6 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
-using System.Reflection;
 using System.Security.Cryptography;
 using System.Threading;
 using System.Threading.Tasks;
@@ -40,7 +39,7 @@ namespace WTelegram
 			{
 				bool hasLength = stream.CanSeek;
 				long transmitted = 0, length = hasLength ? stream.Length : -1;
-				bool isBig = hasLength ? length >= 10 * 1024 * 1024 : true;
+				bool isBig = !hasLength || length >= 10 * 1024 * 1024;
 				int file_total_parts = hasLength ? (int)((length - 1) / FilePartSize) + 1 : -1;
 				long file_id = Helpers.RandomLong();
 				int file_part = 0, read;
@@ -92,7 +91,7 @@ namespace WTelegram
 				await Task.WhenAll(remainingTasks); // wait completion and eventually propagate any task exception
 				if (!isBig) md5.TransformFinalBlock(Array.Empty<byte>(), 0, 0);
 				return isBig ? new InputFileBig { id = file_id, parts = file_total_parts, name = filename }
-					: new InputFile { id = file_id, parts = file_total_parts, name = filename, md5_checksum = md5.Hash };
+					: new InputFile { id = file_id, parts = file_total_parts, name = filename, md5_checksum = Convert.ToHexString(md5.Hash).ToLower() };
 			}
 		}
 
diff --git a/src/Helpers.cs b/src/Helpers.cs
index 3231d95..50b445e 100644
--- a/src/Helpers.cs
+++ b/src/Helpers.cs
@@ -241,7 +241,7 @@ namespace WTelegram
 			public long? ContentLength;
 			protected readonly Stream _innerStream;
 			public override bool CanRead => _innerStream.CanRead;
-			public override bool CanSeek => _innerStream.CanSeek;
+			public override bool CanSeek => ContentLength.HasValue || _innerStream.CanSeek;
 			public override bool CanWrite => _innerStream.CanWrite;
 			public override long Length => ContentLength ?? _innerStream.Length;
 			public override long Position { get => _innerStream.Position; set => _innerStream.Position = value; }
diff --git a/src/TL.Schema.cs b/src/TL.Schema.cs
index 6efec45..eff054b 100644
--- a/src/TL.Schema.cs
+++ b/src/TL.Schema.cs
@@ -150,7 +150,7 @@ namespace TL
 		/// <summary>Full name of the file</summary>
 		public string name;
 		/// <summary>In case the file's <a href="https://en.wikipedia.org/wiki/MD5#MD5_hashes">md5-hash</a> was passed, contents of the file will be checked prior to use</summary>
-		public byte[] md5_checksum;
+		public string md5_checksum;
 
 		/// <summary>Random file identifier created by the client</summary>
 		public override long ID { get => id; set => id = value; }
@@ -5481,7 +5481,7 @@ namespace TL
 		/// <summary>Number of saved parts</summary>
 		public int parts;
 		/// <summary>In case <a href="https://en.wikipedia.org/wiki/MD5">md5-HASH</a> of the (already encrypted) file was transmitted, file content will be checked prior to use</summary>
-		public byte[] md5_checksum;
+		public string md5_checksum;
 		/// <summary>32-bit fingerprint of the key used to encrypt a file</summary>
 		public int key_fingerprint;
 
@@ -10806,7 +10806,7 @@ namespace TL
 		/// <summary>Secure file part count</summary>
 		public int parts;
 		/// <summary>MD5 hash of encrypted uploaded file, to be checked server-side</summary>
-		public byte[] md5_checksum;
+		public string md5_checksum;
 		/// <summary>File hash</summary>
 		public byte[] file_hash;
 		/// <summary>Secret</summary>