Pope Francis, the current leader of the Roman Catholic Church, is known for his relative openness toward conversations long considered taboo in the church, such as LGBTQ issues, contraceptives and abortion. Now the pope is questioning the church’s longstanding rule that priests cannot be married.

In an interview published Thursday in the German newspaper Die Zeit, Francis suggested that married men could be ordained as priests in rural communities facing shortages of priests, according to the Associated Press.

“We must consider if viri probati is a possibility,” he said in the interview. “Then we must determine what tasks they can perform, for example, in remote communities.”

The Latin phrase the pope used translates to “tested man.” It’s the idea that married men who have proven their faith and are actively involved in the Catholic Church could become priests.

For centuries, the church has required that priests be unmarried and celibate in order to dedicate themselves fully to serving God. The celibacy rule is explained in the Church’s Code of Canon Law:

Clerics are obliged to observe perfect and perpetual continence for the sake of the kingdom of heaven and therefore are bound to celibacy which is a special gift of God by which sacred ministers can adhere more easily to Christ with an undivided heart and are able to dedicate themselves more freely to the service of God and humanity.

While Pope Francis acknowledged the idea of allowing faithful married men to become priests, he also emphasized in the interview that men who are already priests would not be allowed to marry, according to CNN. Basically, once a single man becomes a priest, he would have to stay celibate and would not have the choice to marry.

The comments are a response to challenges facing Latin American churches, especially Brazil. The AP reported that Francis’s longtime friend, Brazilian Cardinal Cláudio Hummes, is promoting viri probati in a country that has just one priest for every 10,000 Catholics. Allowing married men to become priests would potentially help alleviate that shortfall.

Pope Francis’s comments definitely bring increased attention to the issue, but the debate over celibacy is nothing new. Clergy members and priests have challenged the celibacy rule for decades, arguing that faithful married men should be allowed to be ordained. In a February 2016 opinion article published in the Catholic Herald, a British Catholic newspaper, reporter Jon Anderson described the Catholic Church as “embroiled in arguments about whether priestly celibacy has a place in today’s world.”

Anderson said opponents of a celibacy requirement believed the rule was out of date and making it harder to encourage young men to join the priesthood.

On the other hand, according to Anderson, people advocating for the rule say that priests should commit themselves fully to God and their faith, instead of sharing themselves with their wives or children. Previous popes St. John Paul II and Benedict XVI both believed that priests needed to remain celibate.

But the church actually already allows exceptions to the rule. A Protestant married priest who converts to Catholicism can stay married while working as a priest, as long as he has his wife’s permission. Some Eastern Catholic churches are also allowed to maintain their tradition of having married priests.