With increasingly prevalent wireless sensors and devices, low power and lossy networks (LLNs) play an essential role in the realization of ubiquitous computing and communication infrastructure, which in turn, leads to enhanced data accessibility and availability. A multicast protocol for LLNs, also referred to as MPL, has been standardized to provide both efficient and reliable communication. Due to the shared wireless medium, lack of tamper resistance, and inherent resource constraints, MPLbased LLNs are vulnerable to various Denial-of-Service attacks. In this paper, we propose a heuristic-based detection scheme, called HED, against the suppression attack in MPL-based LLNs, where a malicious node multicasts a series of spoof data messages with continuous sequence numbers to prevent normal nodes from accepting valid data messages and cause them to delete cached data messages. The simulation results show that the proposed scheme is a viable approach against suppression attack.