Network calculus has been proposed and customized as framework for worst case analysis in wireless sensor networks in [1]. It has been demonstrated that this so-called sensor network calculus is an effective means to calculate maximum message transfer delays, maximum buffer requirements at the sensor nodes as well as lower bounds on duty cyles. Yet, so far only a single sink was accomodated for in the respective models. In this paper, we describe how sensor network calculus can be enhanced to also cover scenarios involving multiple sinks.