diff --git a/phpseclib/Net/SFTP.php b/phpseclib/Net/SFTP.php
index 8ad031e1..34741831 100644
--- a/phpseclib/Net/SFTP.php
+++ b/phpseclib/Net/SFTP.php
@@ -1024,7 +1024,7 @@ class SFTP extends SSH2
             uasort($contents, array(&$this, '_comparator'));
         }
 
-        return $raw ? $contents : array_keys($contents);
+        return $raw ? $contents : array_map('strval', array_keys($contents));
     }
 
     /**