T must be contravariantly valid

What is wrong with this?

interface IRepository<out T> where T : IBusinessEntity
{
    IQueryable<T> GetAll();
    void Save(T t);
    void Delete(T t);
}

It says:

Invalid variance: The type parameter 'T' must be contravariantly valid on 'MyNamespace.IRepository.Delete(T)'. 'T' is covariant.