Post Malone was on his “best behavior” as he stepped into the hallowed circle and made his Grand Ole Opry debut on Wednesday night (Aug. 14).

That meant a lot of changes from a normal Posty show: He appeared onstage without his two signature vices — a beer can in one hand, a lit cigarette in the other — and kept his language PG throughout the broadcasted set.

He did have a red Solo cup in his hand during one portion of the performance, and joking assured the audience, “This is apple juice.”

Avoiding foul language took some effort on the singer’s part, though, and halfway through the night, he admitted to the audience that he’d made a slip.

“Is everyone having fun tonight?” he asked the crowd, following his performance with surprise guest John Michael Montgomery.

“I’m not gonna cuss. I’m having the freaking best time of my life that I’ve had,” he went on to say.

But keeping his language Opry-friendly doesn’t come naturally to the singer, and in fact, by that point in the show, he’d already accidentally let one mild oath fly.

“Have I cussed already?” he asked towards someone offstage. “Just once? Nah, just one is fine I think. I’m on my best behavior tonight, ladies and gentlemen.”

That curse word came early on in his set, when he was telling his crowd how much he loved them, and he encouraged them to “keep kicking a–.” Though that language technically violated Opry standards, the sentiment was pretty wholesome.

You can see how it all went down below in the Opry’s livestream of Post’s show. The language incident takes place at around the :32 minute mark.

The Grand Ole Opry’s shows are intentionally family-friendly, and the venue has a code of conduct that it expects all performing artists to adhere to, including keeping their language tame. That’s partially because the shows are broadcast on radio, meaning that they must adhere to FCC broadcast standards on obscenity, profanity and indecent speech.

Country fans got a reminder of the Opry code of conduct earlier this year, when Elle King took the stage at an Opry-mounted Dolly Parton tribute. King was visibly intoxicated during her time onstage, admitting that she was “f–king hammered” and heckling the crowd as she flubbed the lyrics to Parton’s song, “Marry Me.”

Post’s language slip was a little more endearing, especially because it seemed to be the result of nerves, not alcohol. When he took the stage, he admitted how nervous he was to be there, especially since Brad Paisley — a childhood hero — introduced him to the stage.

“I am so terrified and beyond honored to be standing right in this spot right here,” he told the crowd on Wednesday night. “My mom’s here tonight.”

Elsewhere in the show, Post brought out Lainey Wilson for the debut performance of their duet, “Nosedive.” Other special guests during Post’s Opry debut included Vince Gill and The War and Treaty.

“Nosedive” is one of the songs on Post’s upcoming country album, F-1 Trillion, which is due to arrive on Friday (Aug. 16).

Carena Liptak is an Associate Editor and staff writer at Taste of Country. She specializes in breaking country music news, interviews and lists. In particular, she’s got a soft spot for sad songs — check out her roundup of the 50 Saddest Country Songs of All Time!