Index: memcache-session.inc
===================================================================
--- memcache-session.inc	(revision 16576)
+++ memcache-session.inc	(working copy)
@@ -57,6 +57,7 @@
     $GLOBALS['memcache_session_last_read'] = array(
       'sid' => $session->sid,
       'value' => $user->session,
+      'uid' => $user->uid,
     );
   }
 
@@ -120,7 +121,7 @@
     // Additionally, check if the session has changed since it was loaded.
     // if not, only write with the same frequency as session_write_interval.
     $last_read = isset($GLOBALS['memcache_session_last_read']) ? $GLOBALS['memcache_session_last_read'] : FALSE;
-    $is_changed = empty($last_read) || $last_read['sid'] != $key || $last_read['value'] != $value;
+    $is_changed = empty($last_read) || $last_read['sid'] != $key || $last_read['value'] != $value || $last_read['uid'] != $user->uid;
 
     if ($is_changed || time() - $user->timestamp > variable_get('session_write_interval', 360)) {
       dmemcache_set($key, $session, ini_get('session.gc_maxlifetime'), 'session');