Can children detect a lie when the liar unintentionally reveals essential information (displaying so-called semantic leakage)? Furthermore, because previous research found that theory of mind (ToM) is a factor in children’s lie production ability, what role does ToM play in their lie detection ability? An experiment was carried out with 128 Dutch-speaking children (4 - 14 years old). Children’s lie detection ability was assessed using a story in which one of the characters produced a lie signalled by semantic leakage. A false-belief task was used to test children’s first-order ToM (Kevin thinks that…) and second-order ToM (Marieke thinks that Kevin thinks that…). Children were 73% accurate in identifying the liar by referring to semantic leakage. Their performance improved with age, with 12-year-olds showing ceiling performance. Finaly, first-order ToM was a significant predictor, even after controlling for age, suggesting that lie production and lie detection partly rely on shared cognitive functions.