switch {
	case strings.HasPrefix(r.URL.Path, peerRESTPrefix):
		writeErrorResponseString(r.Context(), w, APIError{
			Code:           "XMinioPeerVersionMismatch",
			Description:    desc,
			HTTPStatusCode: http.StatusUpgradeRequired,
		}, r.URL)
	case strings.HasPrefix(r.URL.Path, storageRESTPrefix):
		writeErrorResponseString(r.Context(), w, APIError{
			Code:           "XMinioStorageVersionMismatch",

	w.Header().Set(xMinIOErrCodeHeader, err.Code)
	w.Header().Set(xMinIOErrDescHeader, "\""+err.Description+"\"")
	writeResponse(w, err.HTTPStatusCode, nil, mimeNone)
}

func writeErrorResponseString(ctx context.Context, w http.ResponseWriter, err APIError, reqURL *url.URL) {
	// Generate string error response.
	writeResponse(w, err.HTTPStatusCode, []byte(err.Description), mimeNone)
}