diff --git a/hooks/ceilometer_hooks.py b/hooks/ceilometer_hooks.py
index 87fd8d1..65b5407 100755
--- a/hooks/ceilometer_hooks.py
+++ b/hooks/ceilometer_hooks.py
@@ -383,6 +383,9 @@ def keystone_joined(relid=None):
     cmp_codename = CompareOpenStackReleases(
         get_os_codename_install_source(config('openstack-origin')))
     if cmp_codename >= 'queens':
+        log("For OpenStack version Queens and onwards Ceilometer Charm "
+            "requires the 'identity-credentials' relation to Keystone, not "
+            "the 'identity-service' relation.", level=WARNING)
         log('Skipping endpoint registration for >= Queens', level=DEBUG)
         return