diff --git a/lib/ajax/service.php b/lib/ajax/service.php
index 366f1ad16ff..ce58f01d026 100644
--- a/lib/ajax/service.php
+++ b/lib/ajax/service.php
@@ -58,6 +58,11 @@ foreach ($requests as $request) {
 
         // Do not allow access to write or delete webservices as a public user.
         if ($externalfunctioninfo->loginrequired) {
+            if (defined('NO_MOODLE_COOKIES') && NO_MOODLE_COOKIES) {
+                error_log('Set "loginrequired" to false in db/service.php when calling entry point service-nologin.php. ' .
+                          'Failed to call "' . $methodname . '"');
+                throw new moodle_exception('servicenotavailable', 'webservice');
+            }
             if (!isloggedin()) {
                 error_log('This external function is not available to public users. Failed to call "' . $methodname . '"');
                 throw new moodle_exception('servicenotavailable', 'webservice');