diff --git a/enrol/externallib.php b/enrol/externallib.php
index 3a0c38f18a1..8f30ad120fe 100644
--- a/enrol/externallib.php
+++ b/enrol/externallib.php
@@ -453,7 +453,11 @@ class core_enrol_external extends external_api {
                                                $params['perpage']);
 
         $results = array();
-        $requiredfields = ['id', 'fullname', 'profileimageurl', 'profileimageurlsmall'];
+        // Add also extra user fields.
+        $requiredfields = array_merge(
+            ['id', 'fullname', 'profileimageurl', 'profileimageurlsmall'],
+            get_extra_user_fields($context)
+        );
         foreach ($users['users'] as $id => $user) {
             // Note: We pass the course here to validate that the current user can at least view user details in this course.
             // The user we are looking at is not in this course yet though - but we only fetch the minimal set of