Indexation of cost of improvement of shares

What will be the tax treatment of short term capital gain arising on sale of shares of an unlisted private limited company? Mr. X has purchased shares of unlisted private limited company in F.Y. 2000-01 which was partly paid up. Paid up value was Rs. 8 per share and face value was Rs. 10 per share. On 31.01.2015 the company called the last call and the call money was paid by Mr. X to the company on 31.01.2015. Now Mr. X has sold his shares to Mr. Y on 17.06.2016. My question is whether the call money paid by Mr. X will form part of cost of improvement while calculating long term capital gain on such shares?