Sophie Turner was "totally surprised" by Joe Jonas' proposal.
The 'Game of Thrones' star was reportedly shocked when the 'Cake By The Ocean' hitmaker got down on one knee but she eagerly accepted their proposal because she's "so in love".
A source said: "Sophie was totally surprised. Joe is a romantic. He is really so in love with Sophie and she's so in love with him."
And despite the pair getting engaged after just under a year together, they aren't "rushing" down the aisle.
Another insider added to Us Weekly magazine: "They are madly in love. She's young but mature and comes from a small English town, so it's not that out of the ordinary and age doesn't create an issue. They are really good together and his friends and family love her and vice versa, but they aren't rushing to get married."
It comes after it was revealed that Joe's friends and family are "thrilled" he's engaged to Sophie.
The source shared: "Everybody's very, very happy for them and their family and friends are all thrilled. Everyone loves them together. She's young but is beyond her years and is crazy, crazy mature. He's never been like this with a girl. He was such a dater before her but their relationship was much different from the start. She was just the one for him."
Sophie announced her engagement on social media on Sunday (15.10.17), where the couple posted matching pictures of their rings.
The 21-year-old star had previously revealed how she likes to keep her relationship as private as possible.
She explained: "I'm in a relationship, but it's a very private relationship. I'm happier than I've been in a very long time. I very much isolated myself for a while and forgot what was fun. Going out with friends, going out to eat, not really having a care.
"And people I've met recently in my life have drawn me out of that. It really helps you own those insecurities. The things I tortured myself about before, I can forget about."