NRules/NRules

Is there a way to properly remove a fact from the sessions memory once inserted?
Simply calling Remove/ TryRemove doesn't actually free any memory...

Minimized example of what I am currently trying to do:

using System;
using NRules;
using NRules.Fluent;
using NRules.Fluent.Dsl;

namespace Playground
{
    class Fact
    {
        public int data { get; set; }
    }

    public class TestRule : Rule
    {

        public override void Define()
        {
            Fact fact = null;
            When()
                .Match<Fact>(() => fact);

            Then()
                .Do(ctx => Console.WriteLine("fact " + fact.data));
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("press any key to start...");
            Console.ReadKey();
            var repository = new RuleRepository();
            repository.Load(x => x.From(typeof(Program).Assembly));

            var factory = repository.Compile();

            var session = factory.CreateSession();

            Console.WriteLine("inserting facts...\n");

            for (int i = 0; i < 1000000; ++i)
            {
                session.Insert(new Fact { data = i });
            }

            // memory usage has now grown to ~800 MB    

            Console.WriteLine("press any key to retract facts...");
            Console.ReadKey();

            foreach (var fact in session.Query<Fact>())
            {
                if (!session.TryRetract(fact))
                {
                    Console.WriteLine("retracting " + fact.data + " failed"); // no output -> no errors
                }
            }

            foreach (var fact in session.Query<Fact>())
            {
                Console.WriteLine("still in memory: " + fact.data + ")"); // no output -> no facts in session
            }

            // memory usage hasn't dropped down again

            Console.WriteLine("\nPress any key to continue...");
            Console.ReadKey();
        }
    }
}