Asynchronous circuits, as any IC, are vulnerable to hardware Trojans (HTs), which might be maliciously implanted in IC designs during outsourced fabrication phases. In this paper, a new testing technique to detect HTs by exploiting the regular side-channel properties of quasi-delay insensitive (QDI) asynchronous circuits is proposed. The technique does not need neither additional circuitry nor significant adjustments in the post-fabrication testing phase. Simulation results show that the proposed technique is able to detect HTs with dimensions smaller than 1% of the original circuit.