diff --git a/protos/voltha_protos/core_adapter.proto b/protos/voltha_protos/core_adapter.proto
index e58aaaa..677abca 100755
--- a/protos/voltha_protos/core_adapter.proto
+++ b/protos/voltha_protos/core_adapter.proto
@@ -23,7 +23,7 @@
 message ChildDeviceFilter {
     string parent_id = 1;
     string serial_number = 2;
-    uint32 onu_id = 3;
+    optional uint32 onu_id = 3;
     uint32 parent_port_no = 4;
 }