diff --git a/phpseclib/Net/SSH2.php b/phpseclib/Net/SSH2.php
index 045d15d4..df0c56e3 100644
--- a/phpseclib/Net/SSH2.php
+++ b/phpseclib/Net/SSH2.php
@@ -2532,7 +2532,7 @@ class Net_SSH2 {
                     break;
                 case NET_SSH2_MSG_CHANNEL_OPEN: // see http://tools.ietf.org/html/rfc4254#section-5.1
                     $this->_string_shift($payload, 1);
-                    extract(unpack('N', $this->_string_shift($payload, 4)));
+                    extract(unpack('Nlength', $this->_string_shift($payload, 4)));
                     $this->errors[] = 'SSH_MSG_CHANNEL_OPEN: ' . utf8_decode($this->_string_shift($payload, $length));
 
                     $this->_string_shift($payload, 4); // skip over client channel