Credit: INFphoto.com

It wasn't exactly a double date.

Ex-spouses Jessica Simpson and Nick Lachey -- each with their current loves Eric Johnson and Vanessa Minnillo, respectively -- accidentally dined for hours at the same Hollywood restaurant on Thursday night.

A witness confirms that the couples arrived separately at The Red O restaurant around 8 p.m. (Each pair was photographed outside the hotspot.) Simpson's mom Tina also joined the star, 30, and her ex-NFL beau, 32. No word on whether the five interacted once inside. See more pics of the exes at dinner.

Lachey, 36, and Minnillo, 29, left around 11pm. Simpson's trio departed about an hour later, the observer adds.

Newlyweds stars Simpson and Lachey divorced in 2006 after four years of marriage.

Does Lachey ever talk about his famous ex-wife with Minnillo, his love of four years? "The past is the past," Minnillo recently sniffed to Parade.com.