Morgan Stanley and Citigroup Inc. have agreed to extend the deadline for determining the fair market value of their Morgan Stanley Smith Barney joint venture, as Morgan Stanley seeks to up its stake in the firm.

Earlier this year, Morgan Stanley said that it intends to increase its stake in the wealth management joint venture by exercising its right to buy another 14% of the firm from Citi, taking its 51% stake to 65%.

Morgan Stanley exercised its call option for an additional stake in the firm on June 1. And, under the terms of the venture, this triggered a process of up to 90 days to determine the purchase price, which is set to expire on Sept. 1. Now, they’ve agreed to extend that deadline to Sept. 10.