Chris Pratt took to Instagram to show some birthday love to his girlfriend, Katherine Schwarzenegger.

In a post captioned:

"Happy Birthday, Chief! Your smile lights up the room. I’ve cherished our time together. Thrilled God put you in my life. Thankful for the laughs, kisses, talks, hikes, love, and care.♥️🍾🎉🎂"

The post displayed six images of Katherine, including two with Pratt - looking extremely happy. This is the first time Pratt has posted his new girlfriend on social media. They have been dating since the summer.

“It’s only been a couple of months, but they’re both serious about the relationship and hopeful for the future,” a source told PEOPLE. “Chris doesn’t just date to date, and neither does Katherine. She’s very excited. Family is very important to both of them, as well as their spirituality. She’s very, very sweet and maternal and great with his son.”

Katherine is, of course, the daughter of Hollywood actor, Arnold Schwarzenegger.