DETROIT (AP) — A federal judge in Detroit has told Michigan it can’t eliminate straight-party voting.

U.S. District Judge Gershwin Drain issued the ruling Wednesday. He argued that not allowing voters to make a single mark on a ballot to pick candidates of one party would lengthen long lines and increase wait times for all voters.

Drain also ruled the change would discriminate against African-American voters because they use straight-party voting at higher rates and frequently cast ballots for Democrats.

Gov. Rick Snyder and other Republicans say a ban would inspire voters to do their homework instead of simply choosing a party.

Nearly half of all Michigan ballots were straight-party during the 2016 election. It’s also common in Republican-friendly counties won by President Donald Trump, such as Ottawa, Allegan, Livingston and Kent.