U.S. President Joe Biden made an error when welcoming the Boston Celtics to The White House on Thursday to celebrate their NBA championship victory.

Biden, 82, appeared to announce the Celtics as “the Bulls” before pausing to ask: “You’re the Celtics, right?” Ahead of the mistake, Biden said: “Welcome to The White House, I don’t know any of these guys behind me but they just showed up. I don’t know where they came from.”

The error drew a laugh from the crowd, and Biden appeared to regain composure as he added: “Not just any champion, but the winningest franchise in league history, and now with a record 18 titles.” Behind Biden, Jayson Tatum and Al Horford struggled to keep a straight face.

Biden then claimed that his nickname was ‘Celtic’ and appeared to show his support for Boston due to being Irish. “You may not know this, but my Secret Service name is ‘Celtic.’ For real, because I’m Irish,” Biden added.

“Everyone behind me is Irish in their heart. From this old Irish Celtic to all you Celtics, congratulations.” Biden then made a joke about his age after referencing that Joe Muzzulla was the youngest head coach to win a championship since Bill Russell in 1969.

“I told him I used to be the youngest and now I’m the oldest. I liked being the youngest better,” said Biden. The Celtics then gifted the president a special ‘No. 46, Biden’ jersey while also handing him a basketball, and he even played a pass to Horford before the ceremony was over.

Biden then paid tribute to the efforts of last season, and summed up the hard work that went into sealing a record title. “Together you guys built one of the deepest teams of all time. Incredible players like Jayson, Jaylen, Derrick and Jrue. Big Al,” Biden said.

“I know it wasn’t easy. You came close more than once. You put in the work, and clocked one of the greatest seasons ever. Sixty four wins and the best record in the league last year. More Points-Per-Possession than any team in NBA history.

“Beating the Heat in 5, the Cavs in 5, and the Pacers in 4. Then you dominated Dallas on both ends of the floor. Now an 18th championship banner hangs in the rafters.

“But you’re hungry for more. A total team effort that you show off the court as well,” President Biden continued. “Working across Boston through your foundations to fight injustice, expand education, register voters, deliver healthcare to help infantas and moms. It matters.”