Former Trump campaign aide Rick Gates has agreed to plead guilty to fraud-related charges and will testify against former colleague and Trump campaign manager Paul Manafort, according to the Los Angeles Times.

Gates was going to plead not guilty after being indicted in October alongside Manafort but now reportedly has reached a deal to cooperate with special counsel Robert Mueller, the Times reported.

Gates served as the deputy campaign manager for the Trump campaign.

Both were indicted for hiding millions in Ukraine-based payments from U.S. authorities.

The plea deal is the latest development surrounding the Mueller’s probe into Russian interference with the 2016 election and if the Trump campaign colluded with Russia.

Mueller also indicted 13 Russian nationals and three groups with charges related to the probe.