Louis Tomlinson went berserk on an internet pest who had been sending really rude messages to his little sister Lottie.
Lottie, 15, is said to have been on the receiving end of messages from the 24-year-old, via text and Twitter, for months.
Among other things, the man is said to have sent her racy chat-up lines and semi-naked pictures.
And when Lottie turned to Louis for help, he called the creep up!
Louis is said to have gone to town on the pest, saying that if he didn’t leave his sister alone, he was going to call the police.
Lottie has since quit Twitter and told her followers, “Coming off Twitter for a bit, bye.”