diff --git a/phpseclib/Net/SSH2.php b/phpseclib/Net/SSH2.php
index 2fddb68a..d3bc7c60 100644
--- a/phpseclib/Net/SSH2.php
+++ b/phpseclib/Net/SSH2.php
@@ -2258,7 +2258,7 @@ class Net_SSH2
                     return false;
                 default:
                     if (is_callable($callback)) {
-                        $callback($temp);
+                        call_user_func($callback, $temp);
                     } else {
                         $output.= $temp;
                     }