The Supreme Court sided with opponents of a Republican-friendly congressional map in Missouri on Thursday, rejecting a plan that could have given the GOP an extra seat in the House of Representatives.

The order, issued without explanation and no noted dissent, will almost certainly mean the state will use a previous map that included six — rather than seven — winnable seats for the GOP.

The one-paragraph decision will affect only a single seat, however, it is an unusual election-related loss for Republicans at the 6-3 conservative Supreme Court. And it undercuts President Donald Trump’s effort to eke an advantage out of state congressional maps across the country to retain Republican control of the House next year.

“The law is the law, the Missouri constitution is clear as was the Missouri Supreme Court,” said Richard von Glahn, executive director of People Not Politicians Missouri, the group that challenged the map and filed the emergency appeal at the Supreme Court. “Over 305,000 Missouri voters — Republicans, Democrats and independents — took action to block this political power grab last fall.”

Aides to Missouri Attorney General Catherine Hanaway, a Republican, did not immediately respond to a request for comment.