Kylie Jenner and Tyga kept their forbidden love a secret for months, waiting to go public when Jenner turned the legal age of 18. The reality star finally celebrated her birthday on Aug. 10, and her boyfriend didn't wait long to ask for her hand in marriage.

"Tyga and Kylie are engaged," a source told HollywoodLife.com, confirming that the ring Jenner has shown off in multiple Instagram posts is an engagement ring. "He gave her that ring and asked her to marry him. They aren't ready to tell everyone so right now they're keeping it a secret from most people."

The aspiring model sported a Cartier ring on her left ring finger in a photo on Thursday. Jenner usually accessorizes with many rings on her fingers, but she seemed to show off the ring casually by writing about her haircut.

Tyga may have put a ring on it, but the couple is in no hurry to walk down the aisle.

"Kylie is very happy," the source said. "They're not in a rush to have a wedding, it's just about knowing they've made the commitment."

Tyga featured Kylie in his new music video for "Stimulated," which dropped earlier this week, and the couple celebrated Jenner's birthday with a romantic getaway to Mexico. He also bought her a Ferrari convertible to celebrate.