diff --git a/includes/session.inc b/includes/session.inc
index fd04de8..57abe12 100644
--- a/includes/session.inc
+++ b/includes/session.inc
@@ -185,7 +185,7 @@ function _drupal_session_write($sid, $value) {
       // Use the session ID as 'sid' and an empty string as 'ssid' by default.
       // _drupal_session_read() does not allow empty strings so that's a safe
       // default.
-      $key = array('sid' => $sid, 'ssid' => '');
+      $key = array('sid' => $sid);
       // On HTTPS connections, use the session ID as both 'sid' and 'ssid'.
       if ($is_https) {
         $key['ssid'] = $sid;