Taylor Swift has gushed over Jack Antonoff for his work on their first collaboration Sweeter Than Fiction.

In a Sunday Instagram post, the Lover singer reflected on her collaborations with the Grammy-winning producer, including Sweeter Than Fiction, which appears as a bonus track on the Tangerine Edition of her re-released album, 1989 (Taylor's Version).

"There you'll stand ten feet tall, I will say 'I knew it all along,'" Taylor captioned photos of herself hugging Jack. "This song has always made me think of my friend Jack. It was the first song we made together and watching him challenge himself and make beautiful art over the years has been the thrill of a lifetime."

She concluded, "How can he be 6 years older than me and also somehow still be my precocious young son? We may never know. Sweeter Than Fiction (My Version) is now available exclusively at Target on Tangerine vinyl."

Sweeter Than Fiction was originally released in 2013 as part of the soundtrack for the British film One Chance. Taylor and Jack have written and produced songs together ever since.

Jack also recently opened up about his professional relationship with the pop icon.

"I could quantify our relationship in very reductive ways about the things we agree on, the sounds we like. But the truth is, we've just grown together," he told Today's Willie Geist. "She put an amazing amount of belief in me. And it's powerful."