The judge presiding over the anticipated trial of two senior aides to Boston Mayor Marty Walsh charged with extortion has ordered that the trial date be moved back two months, from this January to March.

Former city tourism director Kenneth Brissette and former intergovernmental affairs director Timothy Sullivan were indicted by federal prosecutors in 2016 and charged with extortion for allegedly pressuring the Boston Calling music festival to hire union labor.

Their trial was expected to begin this January, but on Monday, the judge overseeing their cases agreed to a motion by the defendants arguing that they needed more time to prepare after federal prosecutors — just over a month before the trial was to start — filed amended charges against them. 

In a second superseding indictment filed about two weeks ago, prosecutors tweaked the wording of the accusations against the men — possibly in response to recent appellate reversals in cases involving similar charges. The U.S. Attorney's Office would not comment on the new indictment.

Specifically, prosecutors removed wording alleging that the defendants illegally sought the hiring of union labor that was "unnecessary" or "superfluous." 

The changes might have seemed small, but the defendants argued that they amounted to a substantial enough change to the charges against them that they were entitled to have time for more discovery and to change a motion to dismiss the case before trial.

U.S. District Judge Leo T. Sorokin agreed, moving the trial date to March 26 and giving the defendants until a week from now to file a revised motion to dismiss.