Days before their union’s contract was set to expire, office cleaners in Maryland, Virginia and Washington, D.C., struck a deal with building landlords, averting a threatened strike.

The four-year deal includes an increase of at least $3.55 in hourly wages for the 9,100 workers in the region, according to a news release from Service Employees International Union 32BJ.

The pay increase will be implemented over the course of the contract, the release said, as cleaners now earn between $12.50 and $18.60. There are about 500 office cleaners in Baltimore represented by the union.

The deal was struck with the Washington Service Contractors Association, the organization that represents office cleaners.

“These men and women proved that collective action has the power to improve jobs and lives, just like other low-wage workers deserve nationwide,” said Jamie Contreras, executive vice president of 32BJ, in a statement.

Workers rallied last week in downtown Baltimore, marching around some of the office buildings they cleaned while chanting in English and Spanish.