In a conventional fixed annuity, idiosyncratic risk is diversified away while systematic longevity risk is borne entirely by the provider. The mortality-indexed annuity on the other hand, transfers systematic longevity risk completely back to the annuitants by fully adjusting benefits to mortality experience. In this paper, we propose the partial mortality-indexed annuity (PMIA), which aims to seek a balance between the two ends of the risk-sharing spectrum. Through a simulation study, we show that the PMIA achieves risk sharing and benefits both the provider and the annuitant.