diff --git a/xos/synchronizer/models/volt.xproto b/xos/synchronizer/models/volt.xproto
index d461623..1db42e4 100644
--- a/xos/synchronizer/models/volt.xproto
+++ b/xos/synchronizer/models/volt.xproto
@@ -97,5 +97,5 @@
     option verbose_name = "vOLT Service Instance";
 
     optional string description = 1 [max_length = 254, db_index = False];
-    optional manytoone onu_device->ONUDevice:volt_service_instances = 1 [db_index = True];
-}
\ No newline at end of file
+    optional manytoone onu_device->ONUDevice:volt_service_instances = 2 [db_index = True];
+}