Why can't the C# compiler infer the types here?

Question

What am I missing here, shouldn't the compiler be able to unambiguously infer the types here?

abstract class Entity {}

class Model<TEntity> where TEntity : Entity {}

class Helper<T> {}


class Test {

    static void Method<TModel, TEntity>(Helper<TModel> param)
        where TModel : Model<TEntity>
        where TEntity : Entity
    {
    }

    class Foo : Entity {}

    public static void Main ()
    {
        Method(new Helper<Model<Foo>>());
    }
}

I get the following error:

a.cs(20,3): error CS0411: The type arguments for method 'Test.Method(Helper)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

Specifying the types at the call-site works, but I'd rather not have to do that.