The Supreme Court has passed up a chance to further narrow the scope of the Voting Rights Act, unexpectedly turning aside a bid to make it harder for voters to challenge alleged racial gerrymanders.

The high court’s ruling Thursday affirmed a challenge to Alabama’s congressional map that alleged its creators diluted the power of Black voters in the state.

Alabama has seven congressional districts. One of them — the only one represented by a Democrat — contains a majority of Black voters, despite the fact that over a quarter of the state’s population is African American. Thursday’s decision will likely force the state to redraw its congressional map to add a second predominantly Black district.

The opinion features an unusual ideological breakdown: Chief Justice John Roberts wrote the court’s majority opinion, joined by the court’s liberal bloc — Justices Sonia Sotomayor, Elena Kagan and Ketanji Brown Jackson. Conservative Justice Brett Kavanaugh also joined most of Roberts’ opinion.

The court’s other conservatives — Justices Clarence Thomas, Samuel Alito, Neil Gorsuch and Amy Coney Barrett — dissented.