Tong Ying-kit is also accused of inciting secession for allegedly driving a motorbike into a crowd of police officers while carrying a pro-independence flag on July 1 last year.
His trial is set to begin later this month, without a jury – on the orders of the secretary for justice.
Tong’s lawyers said it is unfair for the alternative charge to be added at this stage, and said the national security judges should not be able hear a case involving the lesser charge.
But the three judges – Esther Toh, Anthea Pang and Wilson Chan – disagreed on both points, saying the move is not unfair to the defendant being as the prosecution will still have to disclose its evidence to the defence before the trial begins.
The court also heard that with the introduction of the alternative charge, the number of prosecution witnesses will rise by two, to 57.
The trial is scheduled to begin on June 23.