diff --git a/cmd/kubeadm/app/util/pkiutil/pki_helpers.go b/cmd/kubeadm/app/util/pkiutil/pki_helpers.go
index 46878c731c0..dac477429c0 100644
--- a/cmd/kubeadm/app/util/pkiutil/pki_helpers.go
+++ b/cmd/kubeadm/app/util/pkiutil/pki_helpers.go
@@ -563,6 +563,8 @@ func CertificateRequestFromFile(file string) (*x509.CertificateRequest, error) {
 
 // NewCSR creates a new CSR
 func NewCSR(cfg CertConfig, key crypto.Signer) (*x509.CertificateRequest, error) {
+	RemoveDuplicateAltNames(&cfg.AltNames)
+
 	template := &x509.CertificateRequest{
 		Subject: pkix.Name{
 			CommonName:   cfg.CommonName,