"Empire" co-stars Grace Gealey and Trai Byers are engaged! Byers, 33, reportedly popped the question during a surprise party he threw for his lady love's 31st birthday at the Chicago restaurant Kinmont on Sunday.

"He surprised her on her birthday," a source told Us Weekly. "He popped the question and she was totally surprised and elated. She can't stop looking at the ring! They celebrated all night."

Another source told E! News that Gealey "thought it would just be the two of them going to dinner, but when they got there, he had arranged a party for about 20 of her friends and family members to surprise her."

Without mentioning his engagement, Byers posted a photo collage from Gealey's party on Instagram, including a pic of him and Gealey smiling - with what looks like a diamond ring on Gealey's finger.

"Had so much fun celebrating @gracegealey's life!! Happy Birthday to an exquisite human being! Thank you @kinmontchicago for hosting us. Amazing spot, wonderful food, UNFORGETTABLE night," he captioned the post.

Us Weekly reported that the co-stars began dating after meeting on the set of Fox's hit show. An insider claimed that there was an instant attraction between the co-stars and people on set were aware of their relationship, saying, when "they all hang out together they'll cuddle and give a kiss, but it's nothing obscene."

Gealey plays Anika Calhoun, Lucious Lyon's fiance and step-mom-to-be of Byers' character Andre Lyon.

"Empire" is up for three Primetime Emmy Awards, including one for Taraji P. Henson, who is nominated for Outstanding Lead Actress in a Drama Series.

Empire returns for a second season on Sept. 23.