diff --git a/certificates.go b/certificates.go
index 05643f7..5c1662c 100644
--- a/certificates.go
+++ b/certificates.go
@@ -132,11 +132,11 @@ func genServerCert(privKey, caPrivKey *rsa.PrivateKey, ca *x509.Certificate, cn
 // return PEM encoded certificate
 func genClientCert(privKey, caPrivKey *rsa.PrivateKey, ca *x509.Certificate, cn string) (issuerPEM *bytes.Buffer, err error) {
 	serialNumberRange := new(big.Int).Lsh(big.NewInt(1), 128)
-	serial, _ := rand.Int(rand.Reader, serialNumberRange)
+	serial, err := rand.Int(rand.Reader, serialNumberRange)
 
 	certLifetimeDays, err := strconv.Atoi(*clientCertExpirationDays)
 	if err != nil {
-		return nil, fmt.Errorf("can't get cert expired value: %w", err)
+		return nil, fmt.Errorf("can't get client certificate expiration value: %w", err)
 	}
 
 	notBefore := time.Now()
diff --git a/main.go b/main.go
index 3c28ff7..7d3aa18 100644
--- a/main.go
+++ b/main.go
@@ -75,7 +75,7 @@ var (
 	logLevel                 = kingpin.Flag("log.level", "set log level: trace, debug, info, warn, error (default info)").Default("info").Envar("LOG_LEVEL").String()
 	logFormat                = kingpin.Flag("log.format", "set log format: text, json (default text)").Default("text").Envar("LOG_FORMAT").String()
 	storageBackend           = kingpin.Flag("storage.backend", "storage backend: filesystem, kubernetes.secrets (default filesystem)").Default("filesystem").Envar("STORAGE_BACKEND").String()
-	clientCertExpirationDays = kingpin.Flag("easyrsa.client-cert.expired", "Certificate client expired period for OpenVPN in days, the period will shrink automatically to CA expirition period").Default("3650").Envar("CLIENT_CERT_EXPIRE").String()
+	clientCertExpirationDays = kingpin.Flag("client-cert.expiration-days", "Expiration period of OpenVPN client certificates in days, the period will shrink automatically to the CA expiration period").Default("3650").Envar("CLIENT_CERT_EXPIRATION_DAYS").String()
 
 	certsArchivePath = "/tmp/" + certsArchiveFileName
 	ccdArchivePath   = "/tmp/" + ccdArchiveFileName