diff --git a/phpseclib/Net/SFTP.php b/phpseclib/Net/SFTP.php
index 934ca44e..fb4a0be4 100644
--- a/phpseclib/Net/SFTP.php
+++ b/phpseclib/Net/SFTP.php
@@ -1917,10 +1917,12 @@ class Net_SFTP extends Net_SSH2
 
             if ($local_start >= 0) {
                 fseek($fp, $local_start);
+                $size-= $local_start;
             } elseif ($mode & NET_SFTP_RESUME_START) {
                 // do nothing
             } else {
                 fseek($fp, $offset);
+                $size-= $offset;
             }
         } elseif ($dataCallback) {
             $size = 0;