NSubstitute mock extension method

I want to do mock extension method, but it does not work. How can this be done?

    public static class RandomExtensions
    {
    public static IEnumerable<int> NextInt32s(this System.Random random, int neededValuesNumber, int minInclusive, int maxExclusive){...}
    }
....
            [Fact]
            public void Select()
            {
                var randomizer = Substitute.For<DefaultRandom>();
                randomizer.NextInt32s(3, 1, 10).Returns(new int[] { 1, 2, 3 });
            }