A straightforward method that accounts for the long-range Lennard-Jones (LJ) terms in constant pressure molecular dynamics simulations is presented. This long-range correction (LRC) consists of an additional applied pressure tensor which is periodically calculated from the difference of instantaneous pressures at the selected cutoff and a very long cutoff. It provides results that are nearly independent of the LJ cutoff distance at negligible additional calculation costs, and is particularly suited for anisotropic systems such as liquid/ liquid interfaces or heterogeneous macromolecules where approximations based on spherically symmetric radial distribution functions are expected to fail. The utility of the method is demonstrated for a series of alkanes and water, and for interfaces including a lipid bilayer. The LRC increases densities and decreases isothermal compressibilities, with the changes larger for alkanes than for water (where the long-range interactions are dominated by electrostatic interactions). While implementation of the LRC will not necessarily improve agreement with a particular experiment, it will provide a baseline for improvements in a parameter set that are consistent with the long-range Lennard-Jones interactions.