diff --git a/phpseclib/Net/SSH2.php b/phpseclib/Net/SSH2.php
index 77befa69..d2da09e0 100644
--- a/phpseclib/Net/SSH2.php
+++ b/phpseclib/Net/SSH2.php
@@ -1721,7 +1721,7 @@ class Net_SSH2 {
                 // see http://tools.ietf.org/html/rfc4256#section-3.2
                 if (strlen($this->last_interactive_response)) {
                     $this->last_interactive_response = '';
-                } else {
+                } else if (defined('NET_SSH2_LOGGING')) {
                     $this->message_number_log[count($this->message_number_log) - 1] = str_replace(
                         'UNKNOWN',
                         'NET_SSH2_MSG_USERAUTH_INFO_REQUEST',
@@ -3193,4 +3193,4 @@ class Net_SSH2 {
         }
         return $this->exit_status;
     }
-}
\ No newline at end of file
+}