Brazil’s Petrobras has unveiled a multi-billion dollar shortfall at its Petros oil workers’ pension fund, potentially adding a new layer of complication to the company’s financial situation.

Petrobras revealed in a securities filing that Petros, the country’s second-largest pension fund, ended 2015 with 22.6 billion reais ($6.7 billion) in unfunded liabilities.

Brazilian law sets a tolerance limit of 6.5 billion reais for any pension fund deficit, meaning that Petrobras and its fund’s beneficiaries have to come up with a solution to cover the remaining 16.1