(5) No compensation shall be awarded under this section unless the plaintiff has claimed such compensation in his plaint: Provided that where the plaintiff has not claimed any such compensation in the plaint, the court shall, at any stage of the proceeding, allow him to amend the plaint on such terms as may be just, for including a claim for such compensation. Explanation.- The circumstance that the contract has become incapable of specific performance does not preclude the court from exercising the jurisdiction conferred by this section.