diff --git a/lib/pagelib.php b/lib/pagelib.php
index 1447623977d..7e173071f40 100644
--- a/lib/pagelib.php
+++ b/lib/pagelib.php
@@ -1609,7 +1609,8 @@ class moodle_page {
         }
 
         $mnetpeertheme = '';
-        if (isloggedin() and isset($CFG->mnet_localhost_id) and $USER->mnethostid != $CFG->mnet_localhost_id) {
+        $mnetvarsok = isset($CFG->mnet_localhost_id) && isset($USER->mnethostid);
+        if (isloggedin() and $mnetvarsok and $USER->mnethostid != $CFG->mnet_localhost_id) {
             require_once($CFG->dirroot.'/mnet/peer.php');
             $mnetpeer = new mnet_peer();
             $mnetpeer->set_id($USER->mnethostid);