JENNIFER ANISTON’s much-delayed wedding to Justin Theroux has hit a new roadblock – his “creepy old-man crush” on 22-year-old Selena Gomez!

“Jen and Justin had a blowout fight after the Vanity Fair post-Academy Awards party, and it was all over Selena,” an insider told The National ENQUIRER.

“Jen was in a booth, showing her friend Amy Adams pictures on her phone of floral and seating arrangements for the wedding, when she looked up and saw Justin trying to dirty dance with Selena!”

As The ENQUIRER has reported, Jen is playing a mentoring role to Selena, with the former Disney cutie reminding 46-year-old Jennifer of herself as a young starlet.

But Selena seems to have sparked a different flame with Jen’s 43-year-old fiancé, who stars in the HBO series “The Leftovers.”

“Jen thought Justin was making a fool of himself by hanging on a girl young enough to be his daughter,” the source said.

“Plus, he was breakdancing and flailing all over the floor, trying to impress Selena. Jen was mortified!”

Justin also reportedly planted a kiss on Selena at the bash – only increasing the tension on his very long engagement to the former “Friends” star.

Added the source: “Jen lit into Justin and told him to get over his creepy old-man crush on Selena. Justin swears he’s just being friendly, but Jen isn’t buying that.  

“Jen knew Justin was a flirt, but she thinks he’s really crossed the line with Selena!”