Minor League players officially joined the MLB Players Association Wednesday after Major League Baseball voluntarily recognized the union as the players’ bargaining representatives.

Less than one week after Commissioner Rob Manfred said the league was prepared to execute an agreement on voluntary recognition, an arbitrator certified the players’ union-authorization cards, making it official.

“Major League Baseball has a long history of bargaining in good faith with unions, including those representing Minor and Major League umpires, and Major League players,” a league spokesperson said in a statement. “We respect the right of workers to decide for themselves whether to unionize. Based on the authorization cards gathered, MLB has voluntarily and promptly recognized the MLBPA as the representatives of Minor League players. We are hopeful that a timely and fair collective bargaining agreement will be reached that is good for the game, Minor League players and our fans.”

The MLBPA had received signed authorization cards from a majority of the more than 5,500 Minor Leaguers as of last week, paving the way for them to join the union.

“I applaud this extraordinary group of young Players and welcome them to the MLBPA,” MLBPA executive director Tony Clark said in a statement. “This historic achievement required the right group of Players at the right moment to succeed. Minor Leaguers have courageously seized that moment, and we look forward to improving their terms and conditions of employment through the process of good faith collective bargaining.”

The MLBPA plans to form a separate bargaining unit for the Minor Leaguers, including its own dues, player representatives and executive board. Negotiations for a collective bargaining agreement are expected to take place this offseason.

Last year, MLB raised the minimum salaries for Minor League players, while the league began requiring teams to provide housing for most Minor Leaguers in 2022.