In a rare appeal to his magisterial authority as the Roman pontiff, Pope Francis stated Thursday that the changes made to the Catholic liturgy by the Second Vatican Council are “irreversible.”

In a lengthy discourse to a group of liturgical experts, the Pope said: “We can affirm with certainty and magisterial authority that the liturgical reform is irreversible.”

Francis was referring to the changes in Catholic rituals that included the celebration of the Mass in the vernacular languages, the priest facing the people, and a more active participation of the congregation.

This is not the first time that Pope Francis has expressed his esteem for the 1970 liturgical reform.

In 2015, Francis voiced his gratitude for the new liturgy on the 50th anniversary of the close of the Second Vatican Council. “Let us give thanks to the Lord for what he has done in his church in these 50 years of liturgical reform. It was really a courageous move by the church to get closer to the people of God so that they could understand well what it does, and this is important for us: to follow Mass like this,” he said.

At that time, Francis also foreshadowed this week’s comments that the reform is “irreversible.”

“You cannot turn back,” he told Roman parishioners. “We have to always go forward, always forward and who goes back is making a mistake.”

Francis’ predecessor, Pope Benedict XVI, held a deep appreciation for the older Mass, which is celebrated in Latin, and made it easier for priests to celebrate Mass according to the “extraordinary” form that Catholics used for centuries prior to the Second Vatican Council.

In a 2007 apostolic letter titled Summorum Pontificum, Pope Benedict stated that the older Roman Missal that was released after the Council of Trent and revised by Pope John XXIII is even now to be “duly honoured for its venerable and ancient usage.”

There have been some tensions over the liturgy even inside the Vatican walls, where reportedly Francis doesn’t always see eye-to-eye with the Church’s top liturgical official, Cardinal Robert Sarah of Guinea, especially regarding the value of the older Mass.

In Thursday’s address, Francis called Catholics to leave behind “disruptive ferments and to “apply integrally” the reform approved by the bishops who took part in the Council.

After the Council, the bishops wanted a liturgy that is “alive” for a Church “fully enlivened by the celebrated mysteries,” Francis said.

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