A new robust error-feedback regulator is proposed for a class of uncertain hybrid systems with periodic jumps, using a hybrid extension of the classical internal model principle. The plant need not be minimum phase, square nor SISO. The proposed regulator contains an internal model composed by two main units, a flow internal model providing the correct input to achieve regulation during flows, and a jump internal model resetting the state of the regulator at each period. Such a structure reminds internal model design for ripple-free regulation of sampled-data systems; an important difference is that here the jump internal model must contain more copies of the relevant dynamics of the exosystem with respect to the flow internal model.