Kinetic treatments of drift tearing modes that match an inner, resonant layer solution to an external MHD solution, can fail to match the ideal MHD boundary condition on the parallel electric field. In this paper we demonstrate how consideration of ion sound and ion Landau damping effects achieves this, placing the theory on a firm footing. The implications for a realistic hot plasma resonant layer model – involving large ion Larmor radius and semi-collisional electron physics (Connor et al., 2012) – are determined.