diff --git a/phpseclib/Net/SSH1.php b/phpseclib/Net/SSH1.php
index 61f0ac75..0a6aa908 100644
--- a/phpseclib/Net/SSH1.php
+++ b/phpseclib/Net/SSH1.php
@@ -434,6 +434,30 @@ class Net_SSH1
      */
     var $curTimeout;
 
+    /**
+     * Log Boundary
+     *
+     * @see Net_SSH1::_format_log
+     * @access private
+     */
+    var $log_boundary = ':';
+
+    /**
+     * Log Long Width
+     *
+     * @see Net_SSH1::_format_log
+     * @access private
+     */
+    var $log_long_width = 65;
+
+    /**
+     * Log Short Width
+     *
+     * @see Net_SSH1::_format_log
+     * @access private
+     */
+    var $log_short_width = 16;
+
     /**
      * Default Constructor.
      *
@@ -1351,8 +1375,6 @@ class Net_SSH1
      */
     function _format_log($message_log, $message_number_log)
     {
-        static $boundary = ':', $long_width = 65, $short_width = 16;
-
         $output = '';
         for ($i = 0; $i < count($message_log); $i++) {
             $output.= $message_number_log[$i] . "\r\n";
@@ -1362,19 +1384,13 @@ class Net_SSH1
                 if (strlen($current_log)) {
                     $output.= str_pad(dechex($j), 7, '0', STR_PAD_LEFT) . '0  ';
                 }
-                $fragment = $this->_string_shift($current_log, $short_width);
-                $hex = substr(
-                           preg_replace(
-                               '#(.)#es',
-                               '"' . $boundary . '" . str_pad(dechex(ord(substr("\\1", -1))), 2, "0", STR_PAD_LEFT)',
-                               $fragment),
-                           strlen($boundary)
-                       );
+                $fragment = $this->_string_shift($current_log, $this->log_short_width);
+                $hex = substr(preg_replace_callback('#.#s', array($this, '_format_log_helper'), $fragment), strlen($this->log_boundary));
                 // replace non ASCII printable characters with dots
                 // http://en.wikipedia.org/wiki/ASCII#ASCII_printable_characters
                 // also replace < with a . since < messes up the output on web browsers
                 $raw = preg_replace('#[^\x20-\x7E]|<#', '.', $fragment);
-                $output.= str_pad($hex, $long_width - $short_width, ' ') . $raw . "\r\n";
+                $output.= str_pad($hex, $this->log_long_width - $this->log_short_width, ' ') . $raw . "\r\n";
                 $j++;
             } while (strlen($current_log));
             $output.= "\r\n";
@@ -1383,6 +1399,20 @@ class Net_SSH1
         return $output;
     }
 
+    /**
+     * Helper function for _format_log
+     *
+     * For use with preg_replace_callback()
+     *
+     * @param Array $matches
+     * @access private
+     * @return String
+     */
+    function _format_log_helper($matches)
+    {
+        return $this->log_boundary . str_pad(dechex(ord($matches[0])), 2, '0', STR_PAD_LEFT);
+    }
+
     /**
      * Return the server key public exponent
      *
diff --git a/tests/Net/SSH1Test.php b/tests/Net/SSH1Test.php
new file mode 100644
index 00000000..dc02c36d
--- /dev/null
+++ b/tests/Net/SSH1Test.php
@@ -0,0 +1,41 @@
+<?php
+/**
+ * @author     Marc Scholten <marc@pedigital.de>
+ * @copyright  MMXIII Marc Scholten
+ * @license    http://www.opensource.org/licenses/mit-license.html  MIT License
+ */
+
+class Net_SSH1Test extends PhpseclibTestCase
+{
+    public function formatLogDataProvider()
+    {
+        return array(
+            array(
+                array('hello world'),
+                array('<--'),
+                "<--\r\n00000000  68:65:6c:6c:6f:20:77:6f:72:6c:64                 hello world\r\n\r\n"
+            ),
+            array(
+                array('hello', 'world'),
+                array('<--', '<--'),
+                "<--\r\n00000000  68:65:6c:6c:6f                                   hello\r\n\r\n" .
+                "<--\r\n00000000  77:6f:72:6c:64                                   world\r\n\r\n"
+            ),
+        );
+    }
+
+    /**
+     * @dataProvider formatLogDataProvider
+     */
+    public function testFormatLog(array $message_log, array $message_number_log, $expected)
+    {
+        $ssh = $this->getMockBuilder('Net_SSH1')
+            ->disableOriginalConstructor()
+            ->setMethods(null)
+            ->getMock();
+
+        $result = $ssh->_format_log($message_log, $message_number_log);
+
+        $this->assertEquals($expected, $result);
+    }
+}