U.S. President Donald Trump has granted a full pardon to George Papadopoulos, a former aide to his campaign who pleaded guilty as part of an investigation into Russian interference in the 2016 presidential election.

Trump also pardoned Alex van der Zwaan, 36, the Dutch son-in-law of Russian billionaire Herman Khan. Van der Zwaan was sentenced to 30 days in jail and a $20,000 fine for lying to U.S. special prosecutor Robert Mueller’s investigators about contacts with a Trump campaign official in 2016.

Their names were included in a wave of pre-Christmas pardons announced by the White House. Trump pardoned 15 people in full and commuted all or part of their sentences to 5 others.

Papadopoulos, 33, was a 2016 Trump campaign adviser. In 2017, he pleaded guilty to lying to FBI agents about the timing and significance of his contacts with people who claimed to have ties to high-ranking Russian officials.

The White House said Papadopoulos was charged with a “technology crime, one count of making false statements” as part of the Mueller investigation, which Trump called a “witch hunt.”

“Today’s pardon helps right the wrong that Mueller’s team has done to so many people,” the White House said.

Recall that in November, Trump pardoned his former national security adviser, Michael Flynn, who pleaded guilty to lying to the FBI about his interactions with the Russian ambassador to the United States in the weeks before Trump’s inauguration in January 2017.