Jessica Biel and Justin Timberlake Credit: Kevin Mazur/; Splash News Online

When it came time for Justin Timberlake to put a ring on it, the "My Love" singer was set on doing it his way.

A source tells Us Weekly Timberlake, 31, "went rogue" when he designed love Jessica Biel's six-carat, vintage-inspired engagement ring.

"Jessica's stylist really wanted Justin to come to her when picking out and designing the ring," the source reveals to Us. "She obviously knows what looks best on Jessica, and what type of things she likes to wear. They talked about it [in advance] and then Justin completely went rogue without telling Jessica's stylist, and decided to design the ring on his own."

The source was quick to note that this doesn't mean Biel, 30, isn't a fan of the bauble her fiance chose. "But I wouldn't necessarily say it fits her style," the insider explains.

Us Weekly first broke the news of the New Year's Eve star and the former *NSYNCer's engagement in January; Timberlake popped the question over the holidays during a Jackson, Wyoming ski trip. The duo refused to confirm their big news, although Biel has since been flaunting her bling proudly.