diff --git a/voltha/templates/_helpers.tpl b/voltha/templates/_helpers.tpl
index e7c87f2..a8c2f05 100644
--- a/voltha/templates/_helpers.tpl
+++ b/voltha/templates/_helpers.tpl
@@ -39,6 +39,7 @@
 - "--backend=etcd"
 - "--pon-subnet=10.38.0.0/12"
 - "--ponsim-comm=grpc"
+- "--core-number-extractor=^.*-([0-9]+)_.*$"
 {{- end }}