It's over for Lena Dunham and Jack Antonoff, a source tells E! News exclusively.

The Girls star and Bleachers frontman, who first started dating in 2012, broke up in December. "It was mutual," our insider says. "Jack and Lena were growing apart and it just made sense for them to end their relationship where it was."

Luckily, their split was far from messy, as the source adds, "They want the best for each other no matter what. They are both moving on."

A rep for both stars confirmed the split to E! News.

Dunham and Antonoff attended their last public event together almost one year ago at a Grammys pre-party. In October 2017, the actress and social justice activist penned an essay about her former beau for Variety. She wrote in part, "It's safe to say that before Jack my life was full of far fewer sights. He showed me the importance of making political statements using your public platform. He showed me the joy of collaboration."