As Senators were sworn in on Thursday for the 116th Congress, Kyrsten Sinema, the Democrat from Arizona, made the unusual choice to take her oath of office using a book containing the texts of the U.S. and Arizona constitutions rather than the Bible or another religious book, as is customary.

In a video of the moment published by The Hill, Vice President Mike Pence read out the oath to Sinema: “Do you solemnly swear to support and defend the Constitution of the United States against all enemies foreign and domestic; that you will bear true faith and allegiance to the same; that you take this obligation freely, without any mental reservation or purpose of evasion; and that you will well and faithfully discharge the duties of the office on which you are about to enter: So help you God?”

Related: With Kyrsten Sinema’s election, LGBT representation in Congress hits double digits

The congresswoman responded, “I do.” The Vice President said he looked forward to working with her.

Legally, it doesn’t matter whether someone used a copy of the Constitution or a religious book to be sworn in to office. However, The Arizona Republic suggested that Sinema’s decision could fuel speculation that she is an atheist. According to the Pew Research Center, Sinema is the only member of Congress who has openly identified herself as being unaffiliated with any religion.

John LaBombard, a spokesman for Sinema, explained the decision by telling The Republic, “Kyrsten always gets sworn in on a Constitution simply because of her love for the Constitution.”

Sinema was recently elected to the U.S. upper chamber as Arizona’s first female senator after serving in the House of Representatives for three terms.

When Sinema was first elected to the House, in 2012, she became the first openly bisexual member of Congress in U.S. history. (During her swearing-in ceremony in 2013, she also used a legal text rather than a religious book.) And she is now only the second senator to identify openly as LGBTQ, the other being Tammy Baldwin, the Democrat from Wisconsin.

Although politicians are supposed to be representatives of the people, the religious makeup of the 116th Congress does not accurately represent the views of the U.S adult population, according to Pew.

Related: In Pictures: The Most Diverse Congress in U.S. History

For example, 88.2 percent of Congress members identify as Christian—in particular, Catholics and Protestants—whereas only about 71 percent of the population at large do. Furthermore, 23 percent of the public identifies as agnostic, atheist or “nothing in particular,” as opposed to just one member of Congress who is openly religiously unaffiliated.

Nevertheless, the latest Congress is one of the most religiously diverse in history, as highlighted by a viral photo that showed the variety of books that have been used to swear in Congress members this year, including a Koran, an Orthodox Bible and the Tanakh, the Hebrew Bible.