Serena Williams is looking back on a hilarious faux pas she made while trying to cash in on her first $1 million check.

While appearing on Thursday’s episode of “Hot Ones,” the retired tennis legend reminisced on the moment she tried to deposit her massive tennis winnings into a drive-thru ATM at a bank early in her career. (“Hot Ones” is produced by First We Feast. First We Feast and HuffPost share a parent company, Buzzfeed Inc.)

After host Sean Evans asked her to confirm if the story was true, Williams explained, “I never really spent a lot of money. I was just so serious. I don’t know what happened to me. I used to be serious.”

She went on to clarify that she was so focused on “want[ing] to win” that her tax person had to keep reminding her to claim her earnings because she “loved the sport” so much that she “never played for money.”

“I never played for money. I played because I loved the sport ... I don’t even know at the time if I wanted to play to be the best, I just wanted to win,” the 23-time Grand Slam champion said.

“And so my tax guy, he would be like, ‘You didn’t get your money?’ I’d be like, ‘Oh, I didn’t get that one in Zurich,’ ‘Oh, I forgot that one in Moscow,’” she continued. “I was playing to win, and if I didn’t win, I was just not thinking. I was just so angry that I wanted to figure out a way to get better and win the next time.”

Then, Williams admitted to trying to cash her first million-dollar check at a drive-thru ATM, saying, “I went through the drive-thru ... the guy was like, ‘Uh, I think you need to come inside for this,’ and I was like, ‘Uh, OK.’”

The mom of two, who shares daughters Adira and Olympia with husband Alexis Ohanian, laughed off the incident as one of those countless “lessons to learn.”

Watch Williams’ full interview below.