Standard & Poor’s downgraded Angola’s credit rating to B after a decline in oil prices curbed government revenue.

S&P lowered the rating from B+, putting the nation’s debt five levels below investment grade, the company said in a statement on Friday. The outlook on the rating was stable.

“We consider that the lower-than-expected Brent oil price assumptions for 2016-2019 are weakening our projections for Angola’s external stocks and flows and the pace of economic growth given the country’s dependence on the oil sector,” S&P said.

Angola, Africa’s largest crude producer after Nigeria, relies on the fuel to generate about 70 percent of taxes and 95 percent of export income. As the price of oil plunged, the government slashed its budget spending, cut fuel subsidies and froze hiring. Government spending accounted for more than a third of Angola’s $129 billion gross domestic product in 2014.

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