Nigeria’s state-owned oil company rebutted claims by Africa’s richest man that it failed to meet its payment obligations to increase its stake in his mega refinery to 20% from 7.2%.

“As a company, NNPC Ltd. periodically assesses its investment portfolio to ensure alignment with our strategic goals,” Nigeria National Petroleum Co. said Monday by text message. “The decision to cap our equity participation in the Dangote Refinery was made several months ago, and we informed the Dangote Refinery at that time,” it said.

On Sunday Aliko Dangote said NNPC no longer owns a 20% stake in the refinery — built to a capacity of 650,000 barrels a day — as it failed to pay for the additional stake by June.

The national oil company previously agreed to buy the 20% stake in the refinery and pay for it with large amounts of crude. According to the company’s most recent financial statements, the NNPC committed 335,000 barrels a day to acquire the stake.

Known supplies of Nigerian barrels in December and January were well below that flow rate, although those deliveries were still when the plant was in the earlier stages of ramping up, according to data from traders compiled by Bloomberg.

Despite being Africa’s largest crude producer, the West African nation currently imports almost all its petroleum products because its refineries have been largely non-operational for decades. The Dangote Refinery based outside Lagos is expected to end that.