}
			var err error
			if privKey.PrivateKey, err = asn1.Marshal(k.Bytes()); err != nil {
				return nil, fmt.Errorf("x509: failed to marshal private key: %v", err)
			}
		} else {
			oid, ok := oidFromECDHCurve(k.Curve())
			if !ok {
				return nil, errors.New("x509: unknown curve while marshaling to PKCS#8")
			}
			oidBytes, err := asn1.Marshal(oid)
			if err != nil {

	case *ecdh.PublicKey:
		publicKeyBytes = pub.Bytes()
		if pub.Curve() == ecdh.X25519() {
			publicKeyAlgorithm.Algorithm = oidPublicKeyX25519
		} else {
			oid, ok := oidFromECDHCurve(pub.Curve())
			if !ok {
				return nil, pkix.AlgorithmIdentifier{}, errors.New("x509: unsupported elliptic curve")
			}
			publicKeyAlgorithm.Algorithm = oidPublicKeyECDSA
			var paramBytes []byte