diff --git a/ceilometer/api/v1.py b/ceilometer/api/v1.py
index 933089d9..d1ca3ac6 100644
--- a/ceilometer/api/v1.py
+++ b/ceilometer/api/v1.py
@@ -64,6 +64,8 @@
 #                                                    selected meter
 # [x] /resources/<resource>/meters/<meter>/volume/max -- max volume for
 #                                                        selected meter
+# [x] /resources/<resource>/meters/<meter>/volume/sum -- total volume for
+#                                                        selected meter
 # [ ] /sources/<source>/meters/<meter>/volume -- total or max volume for
 #                                                selected meter
 # [ ] /users/<user>/meters/<meter>/volume -- total or max volume for selected