If a testator directs in his will the purchase of an annuity, the beneficiaries to whom the income thereof is to be paid may not elect to take the capital sum directed to be used for the purchase of such annuity in lieu thereof, unless the will expressly confers such right or except as the will expressly provides for the purchase of an assignable annuity. But nothing contained herein shall impair the right of election by a surviving spouse under 5-1.1 or 5-1.1-A.