According to a new report by In Touch, the former That 70's Show co-stars have actually been engaged since the summer.
"It happened over the summer," their source spills. "His whole family had come out to California for Mila's birthday [on Aug. 14], and he did it then."
Apparently, they couldn't go public with their engagement until Ashton's divorce from Demi Moore was final, which just happened last month.
That theory seems to be supported by a recent sighting of the couple, where E! News reports that Mila was wearing a ring on her ring finger.
"She was wearing a small ring on her left hand. It was petite, but still noticeable and pretty," a witness tells the site.
So far, no official word from the couple...