Janitors who clean Twitter’s headquarters in San Francisco are on strike ahead of their union contract ending.

Members of the SEIU Local 87, a custodians union in California, began their strike at 6am in San Francisco on Dec 6, according to a statement from the California Labor Federation. The union says its contract with the social media company’s janitorial contractor ends on Dec 9. Organisers claim Twitter’s new contractor has refused to rehire existing workers, which is required by San Francisco law.

The janitors are picketing to protest management’s refusal to fairly negotiate, Elizabeth Strater, the communications director for the Federation, a coalition of the state’s unions, said in a statement.

“Twitter doesn’t seem to understand how important it is to keep a clean house and respect the people who take out the trash,” she said.

San Francisco law mandates new contractors for security and janitorial services hire existing workers for at least 90 days after the transition from one contract to the next. Workers who are not hired for this time period can seek back pay and benefits for whatever portion of the transition period they were not employed.

A representative for Twitter didn’t immediately respond to request for comment. The majority of Twitter’s communications team was fired after Elon Musk acquired the company last month.

 - Bloomberg