diff --git a/server/src/api.rs b/server/src/api.rs
index ddb93e1..72a40ab 100644
--- a/server/src/api.rs
+++ b/server/src/api.rs
@@ -292,9 +292,10 @@ impl From<&Certificate> for CertInfo {
             .join(" ");
         let opts = opts.trim();
         let renew_command = format!(
-            "ssh-keygen -s ./ca_key {host_key} -I {} -n {} -V {:#x}:{:#x} {opts} {}.pub",
+            "ssh-keygen -s ./ca_key {host_key} -I {} -n {} -z {} -V {:#x}:{:#x} {opts} {}.pub",
             escape(cert.key_id().into()),
             escape(cert.valid_principals().join(",").into()),
+            cert.serial() + 1,
             cert.valid_after(),
             expiry_date.as_secs(),
             escape(cert.key_id().into())