diff --git a/phpseclib/Net/SFTP.php b/phpseclib/Net/SFTP.php
index 2614937b..eacfb674 100644
--- a/phpseclib/Net/SFTP.php
+++ b/phpseclib/Net/SFTP.php
@@ -1681,15 +1681,18 @@ class Net_SFTP extends Net_SSH2 {
             }
 
             if ($length > 0 && $length <= $offset - $size) {
-                if ($local_file === false) {
-                    $content = substr($content, 0, $length);
-                } else {
-                    ftruncate($fp, $length);
-                }
                 break;
             }
         }
 
+        if ($length > 0 && $length <= strlen($content)) {
+            if ($local_file === false) {
+                $content = substr($content, 0, $length);
+            } else {
+                ftruncate($fp, $length);
+            }
+        }
+
         if ($local_file !== false) {
             fclose($fp);
         }