The National Labor Relations Board on Wednesday adopted a rule that will speed union-organizing elections in private-sector workplaces, ushering in some of the biggest procedural changes in decades and scoring a win for unions that say scheduling a vote often takes too long.

The board’s two Democrats approved the rule through electronic voting, while the lone Republican symbolically rejected it by choosing not to vote. The rule takes effect April 30.

The approval drew immediate backlash from employers, who said it leaves them inadequate time to respond to unionization campaigns and limits their rights to legally challenge elections before employee voting occurs.

The U.S. Chamber of Commerce has filed a lawsuit Tuesday night to challenge what it called the “ambush election rule.” The suit, filed in the U.S. District Court for the District of Columbia, claims the rule deprives employers of a fair opportunity to explain to employees the costs of unionizing. The Coalition for a Democratic Workplace is also a plaintiff in the suit.

Labor officials welcomed but downplayed the new rule’s potential impact and said more needs to be done to protect workers’ rights. AFL-CIO President Richard Trumka called the rule a “modest but important step” to help ensure workers get a fair chance to vote on forming a union.