CustomSparkActivator.cs

    public class CustomSparkActivator: IActivator
    {
        private readonly ISparkViewEngine _engine;
        public AlsSparkActivator(ISparkViewEngine engine)
        {
            _engine = engine;
        }

        public void Activate(IEnumerable<IPackageInfo> packages, IPackageLog log)
        {
            ((SparkSettings) _engine.Settings).SetAutomaticEncoding(false);
        }
    }

CustomSparkPolicy.cs

    [Policy]
    public class CustomSparkPolicy: IConfigurationAction
    {
        public void Configure(BehaviorGraph graph)
        {
            var activators = graph.Services.ServicesFor<IActivator>().ToList();
            var activator = ObjectDef.ForType<CustomSparkActivator>();
            activators.Insert(activators.FindIndex(x => x.Type == typeof(SparkPrecompiler)), activator);
            graph.Services.Clear(typeof (IActivator));
            activators.Each(x => graph.Services.AddService(typeof (IActivator), x));
        }
    }