Pope Francis is preparing an address on “fake news” expected to tackle the thorny issue of journalistic integrity in a speech marking World Communications Day.

Francis announced his choice of topic in September, saying the message would be delivered Wednesday — the Catholic feast day of Francis de Sales, patron saint of journalists.

“I have chosen this theme for World Communications Day 2018: ‘The truth will set you free’ (John 8:32). Fake news and journalism for peace,” the pontiff tweeted.

According to a Vatican news release in September, the pope’s address is expected to promote “professional journalism” over and against “fake news.” The term, made famous by President Donald Trump, was defined by the Vatican’s Secretariat for Communication as “baseless information that contributes to generating and nurturing a strong polarization of opinions.”

The pontiff has some personal experience with fake news. During the 2016 election, a satirical news website asserted that Francis endorsed Trump for president. The story was patently false, but became one of the most widely circulated fake news stories on Facebook in advance of the election, according to BuzzFeed.

Francis has railed against “fake news” and misleading reporting in the past. During a meeting with journalists at the Vatican in December, he urged reporters not to fall prey to “sins of communication.”

According to Newsweek, he explained such “sins” include “disinformation, or giving just one side, calumny that is sensationalized, or defamation, looking for things that are old news and have been dealt with and bringing them to light today.” He added: “They are very grave sins, which damage the heart of the journalist and harm people.”

The address comes just days after the pope said sexual abuse victims in Chile were guilty of “calumny” for accusing Bishop Juan Barros of helping to cover up the sex crimes of a priest who is one of Chile’s most notorious pedophiles. Victims reportedly told church authorities about the abuse by the Rev. Fernando Karadimas as early as 2002, but it was only after they went public with their stories in 2010 that a Vatican investigation stripped Karadimas of his ministry.