diff --git a/src/Renci.SshNet/Abstractions/ThreadAbstraction.cs b/src/Renci.SshNet/Abstractions/ThreadAbstraction.cs
index f1ed202ae..fe6e3e218 100644
--- a/src/Renci.SshNet/Abstractions/ThreadAbstraction.cs
+++ b/src/Renci.SshNet/Abstractions/ThreadAbstraction.cs
@@ -36,6 +36,8 @@ public static void ExecuteThreadLongRunning(Action action)
         /// <param name="action">The action to execute.</param>
         public static void ExecuteThread(Action action)
         {
+            if (action == null)
+                throw new ArgumentNullException("action");
 #if FEATURE_THREAD_THREADPOOL
             System.Threading.ThreadPool.QueueUserWorkItem(o => action());
 #elif FEATURE_THREAD_TAP
diff --git a/src/Renci.SshNet/Sftp/SftpFileStream.cs b/src/Renci.SshNet/Sftp/SftpFileStream.cs
index 853010cb0..cc66677f5 100644
--- a/src/Renci.SshNet/Sftp/SftpFileStream.cs
+++ b/src/Renci.SshNet/Sftp/SftpFileStream.cs
@@ -362,7 +362,7 @@ public override int Read(byte[] buffer, int offset, int count)
                         {
                             // copy remaining bytes to read buffer
                             _bufferLen = data.Length - bytesToWriteToCallerBuffer;
-                            Buffer.BlockCopy(data, count, _readBuffer, 0, _bufferLen);
+                            Buffer.BlockCopy(data, bytesToWriteToCallerBuffer, _readBuffer, 0, _bufferLen);
                         }
                     }
                     else