How to use boolean fuction in Where on QueryOver API

Im trying to use the SQL function CONSTAINS to filter some data on QueryOver API.

The main issue is i cant use SqlFunction in where clause, this does not compile, because a ICriterion is needed.

var result = Session.QueryOver<Individual>()
    .Where(Projections.SqlFunction(
        "FullTextContains", NHibernateUtil.Boolean,
        Projections.Property<Individual>(x => x.LastName),
        Projections.Constant("something")))
        .List();

I tried to match it to a TRUE constant, but when the query is executed it generates syntax error, because the CONSTAINS function cant be used with equals operator.

var result = Session.QueryOver<Individual>()
    .Where(Restrictions.Eq(Projections.SqlFunction(
        "FullTextContains", NHibernateUtil.Boolean,
        Projections.Property<Individual>(p => p.LastName),
        Projections.Constant("something")), true))
        .List();

How can i use a boolean sql function directly in where expression on QueryOver API?