diff --git a/library/Zend/Session.php b/library/Zend/Session.php
index 6378cbf612..682601a4c5 100644
--- a/library/Zend/Session.php
+++ b/library/Zend/Session.php
@@ -422,8 +422,6 @@ public static function start($options = false)
     {
         // Check to see if we've been passed an invalid session ID
         if ( self::getId() && !self::_checkId(self::getId()) ) {
-            // Generate a valid, temporary replacement
-            self::setId(md5(self::getId()));
             // Force a regenerate after session is started
             self::$_regenerateIdState = -1;
         }
@@ -434,6 +432,11 @@ public static function start($options = false)
         }
 
         if (self::$_sessionStarted) {
+            // Generate valid session id
+            if (self::$_regenerateIdState === -1) {
+                self::regenerateId();
+            }
+            
             return; // already started
         }
 
@@ -664,7 +667,7 @@ public static function setId($id)
         if (!self::$_unitTestEnabled && defined('SID')) {
             /** @see Zend_Session_Exception */
             require_once 'Zend/Session/Exception.php';
-            throw new Zend_Session_Exception('The session has already been started.  The session id must be set first.');
+            throw new Zend_Session_Exception('The session has already been started. The session id must be set first.');
         }
 
         if (!self::$_unitTestEnabled && headers_sent($filename, $linenum)) {