diff --git a/docker/with-external-db/postgres.env b/docker/with-external-db/postgres.env
index bbf0de1f..bc551fd4 100644
--- a/docker/with-external-db/postgres.env
+++ b/docker/with-external-db/postgres.env
@@ -2,3 +2,4 @@ POSTGRES_USER="postgres"
 POSTGRES_PASSWORD="password"
 POSTGRES_MULTIPLE_DATABASES="app,logto"
 EXTERNAL_DB_CERT="-----BEGIN CERTIFICATE-----MIIC....eRiu-----END CERTIFICATE-----"
+EXTERNAL_DB_CERT_KEY="<DB certificate private key contents>"