return Collections.unmodifiableMap(new PropertiesAsMap(getMavenSession().getSystemProperties()));
    }

    @Nonnull
    @Override
    public Map<String, String> getEffectiveProperties(@Nullable Project project) {
        HashMap<String, String> result = new HashMap<>(getSystemProperties());
        if (project != null) {
            result.putAll(project.getModel().getProperties());
        }