diff --git a/cmd/relayproxy/service/gofeatureflag.go b/cmd/relayproxy/service/gofeatureflag.go
index ce1dcbf6389..e527351e120 100644
--- a/cmd/relayproxy/service/gofeatureflag.go
+++ b/cmd/relayproxy/service/gofeatureflag.go
@@ -319,6 +319,7 @@ func initNotifier(c []config.NotifierConf) ([]notifier.Notifier, error) {
 		case config.SlackNotifier:
 			if cNotif.WebhookURL == "" && cNotif.SlackWebhookURL != "" { // nolint
 				zap.L().Warn("slackWebhookURL field is deprecated, please use webhookURL instead")
+				cNotif.WebhookURL = cNotif.SlackWebhookURL // nolint
 			}
 			notifiers = append(notifiers, &slacknotifier.Notifier{SlackWebhookURL: cNotif.WebhookURL})