Benny Blanco has recalled how "grumpy" Selena Gomez "almost didn't come" to the location where he planned to propose.

Last December, the record producer and Lose You to Love Me singer announced they were engaged after dating for just over a year.

During an appearance on The Tonight Show Starring Jimmy Fallon on Thursday, host Jimmy asked Selena whether she had any clue that Benny was about to pop the question.

"We had to do a lot of promo for the album. So, I woke up, and I was very confused on what was happening, on where we were going, because it seemed kind of far," she began. "So, I'm kind of a little grumpy. I'm, like, tired... I said, 'After this shoot, I'm going to go hang out with my friends.' And he starts, I guess, going, 'O.K., sure. We'll see when you get here.'"

Benny went on to recall how Selena nearly skipped their plans to meet up that day.

"She almost didn't even come. She was like, 'I really don't feel that well. I think I'm just going to stay home today. Can't we just make up the shoot another day?' And I was like, 'Uhh...' I'm trying to figure out a way to do...," the 37-year-old continued. "First of all, getting engaged to someone is the craziest thing in the world. It's like, right before you're going to tell someone you're going to be married to them forever. They're like, 'Show me how good you can lie to me.' It's the hardest... She was just upset with me because the day before, I was making bad lies."

Benny proposed with a stunning six-carat marquise diamond ring.

And the prolific songwriter admitted that it was hard keeping the ring a secret from Selena.

"It was in a box and I had it hidden in a bag that I thought no one would go in. It was the scariest week of my life," he added.

Elsewhere in the conversation, Jimmy asked the couple whether they have started planning the wedding.

In response, Selena emphasised that they are currently focused on promoting their new collaborative album, I Said I Love You First, which drops on Friday.

"We're definitely not planning exactly at this moment, but we do want to make sure that the music is good," the 32-year-old smiled.