diff --git a/lib/accesslib.php b/lib/accesslib.php
index 0a918be4e92..492e24f807a 100755
--- a/lib/accesslib.php
+++ b/lib/accesslib.php
@@ -2764,6 +2764,8 @@ function isguestuser($user = NULL) {
  * @return bool
  */
 function is_guest($context, $user = NULL) {
+    global $USER;
+
     // first find the course context
     $coursecontext = get_course_context($context);