Devices in Low Power and Lossy Networks (LLNs) based Internet of Things (IoT) systems have energy, memory and processing constraints. For LLNs, IETF standardized a light-weight routing protocol referred to as RPL. The energy efficiency of RPL routing protocol has been under investigation in prior studies but its stability issue is recently identified. The stability of RPL is critical for its energy efficient and application oriented routing operation. In RPL, child nodes select best parent towards the sink node based on some Objective Function (OF). Current OFs proposed for RPL result in unstable operation of RPL due to frequent route changes. Consequently, high control traffic is generated to re-construct routes which consumes scarce energy resources and thus reduces the network lifetime. In this paper, a novel OF for RPL is proposed which exploits channel adaptability and stability provided by ETX and HOP routing OFs, respectively. The proposed enhancement of RPL is implemented in Contiki operating system and its analysis is carried out in Cooja simulator. The analysis suggests reduction in frequent parent changes, control traffic and energy consumption, thereby improves RPL stability and energy efficiency.