The Hunger Games actor, who has been dating Cyrus on and off for more than two years, has reportedly told friends that he is sick of looking after her after she parties too hard.
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A friend told Us Weekly magazine: "She gets pretty crazy. She's always out in skimpy outfits and writhing on Liam... Sometimes he looks embarrassed for her."
Another source claimed that Hemsworth is fond of his girlfriend's "fun-loving side", but added that he sometimes "gets concerned too" that she parties too hard.
Cyrus has previously implied that she hates having to "apologise" for her behaviour, saying that she wants to "rock as hard as the guys".
Hemsworth said earlier this year that Cyrus makes him "really happy", also revealing that he tried to be "professional" when they first met on the set of The Last Song but admitting that he couldn't help but fall for her.
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Watch Liam Hemsworth in the trailer for The Hunger Games below: