Ashton Kutcher has a new role: strict step-dad. The Punk'd star is said to be worried about Bruce Willis and Demi Moore's daughter, Rumer, and her growing friendship with the exhaustion-prone Lindsay Lohan.

Kutcher thinks Lohan is a bad influence on his 18-year-old stepdaughter, reports Life & Style Weekly. The pair has been attached at their designer-clad hips recently, shopping in Beverly Hills, attending Rumer's birthday bash at Dolce and even kissing for photographers on the red carpet at the American Cinematheque Award gala honoring George Clooney on Oct. 13.

The pair were introduced by Rumer's famous father – who produced Lohan's movie Just My Luck – and Lohan even vacationed with the Willis family last summer on Parrot Cay island in Turks and Caicos.

But their sudden turn as BFFs has Kutcher worried.

"Education is very important to Ashton," a source tells the mag, "and he's afraid Rumer will think partying is better than studying. Rumer can't stop gushing about how cool Lindsay is. [She] feels honored by Lindsay's attention."

Perhaps Kutcher would have a little more parental authority if he wasn't know as the trucker-hat wearing dude who spent a whole movie looking for his car.

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