We consider in this paper the decision fusion problem for a wireless sensor network (WSN) operating in a fading environment. In particular, we develop channel-aware decision fusion rules for a resource constrained WSN where decisions from local sensors may go through multi-hop transmission to reach a fusion center. Each relay node employs a binary relay scheme whereby the relay output is inferred from the channel impaired observation received from its source node. This estimated binary decision is subsequently transmitted to the next node until it reaches the fusion center. Under a flat fading channel model, we derive the optimum fusion rules at the fusion center for the following two cases. In the first case, we assume that the fusion center has knowledge of the fading channel gains at all hops; while in the second case, assuming a Rayleigh fading model, we derive fusion rules utilizing only the fading channel statistics. We show that both optimum decision fusion statistics reduce to respective simple nonlinearities in the low channel SNR regime that are easy to implement. Performance evaluation, including a study of the robustness of the fusion statistics with respect to unknown system parameters, is conducted through simulations.