diff --git a/northbound/server.go b/northbound/server.go
index 2e45ee2b91476ad5d3694eb0650a42dc14da707e..1463f95b9823b3e55321544867ea3a06b8687ba6 100644
--- a/northbound/server.go
+++ b/northbound/server.go
@@ -115,6 +115,8 @@ func fillOnds(pnd nucleus.PrincipalNetworkDomain) (*ppb.OrchestratedNetworkingDe
 
 func fillSbis(pnd nucleus.PrincipalNetworkDomain) (*ppb.SouthboundInterfaces, error) {
 	sbis := make(map[string]*ppb.SouthboundInterface)
+	sbiLock.RLock()
+	defer sbiLock.RUnlock()
 	sbic := pnd.GetSBIs().(*nucleus.SbiStore)
 	for _,id := range sbic.UUIDs() {
 		sbi, err := sbic.Get(id)