Fitch Ratings downgraded the credit scores of Fannie Mae and Freddie Mac to AA+ from AAA, a day after it cut the US sovereign credit rating.

The downgrades of the two government-sponsored enterprises are consistent with its downgrade of US government debt, Fitch said in a press release on Wednesday. The move was “not being driven by fundamental credit, capital or liquidity deterioration at the firms,” it said.

Fannie Mae and Freddie Mac benefit from implicit government support, Fitch said. The two enterprises help to backstop the multi-trillion dollar market for US home mortgages.

Fannie Mae and Freddie Mac didn’t immediately respond to a request for comment.