The Roman Catholic Church’s teaching that women cannot be ordained as priests is likely to last forever, Pope Francis said on Tuesday as he flew back to Rome from Sweden.

Francis had traveled to Sweden for a historic ceremony commemorating the year leading up to the 500th anniversary of the Protestant Reformation. He was embraced at an ecumenical church service by the primate of the Church of Sweden, Archbishop Antje Jackelen, who is a woman.

Francis has said before that the Catholic Church’s ban on ordaining women as priests is a closed matter. But questions arose about his intentions after he established a commission to study whether women could be ordained as deacons. (Members of the commission were named in August.)

In a news conference aboard the pope’s plane, a Swedish journalist referred to Archbishop Jackelen and asked whether it was realistic to think that there might be female priests in the next few decades.