diff -u b/modules/system/system.install b/modules/system/system.install
--- b/modules/system/system.install
+++ b/modules/system/system.install
@@ -3179,6 +3179,7 @@
   // Force to write again the current session to have it hashed.
   drupal_save_session(TRUE);
   global $user;
+  drupal_static_reset('drupal_session_last_read');
   _drupal_session_write(session_id(), $user->session);
   drupal_save_session(FALSE);