In MBE(n) calculations on proteins, we demonstrated that low-dielectric boundary conditions are necessary to obtain converged results in the presence of ionic residues. Dielectric boundaries can be implemented by means of a polarizable continuum model (PCM), using a dielectric constant ε = 4 as in previous work. Re-sults in Fig. show that MBE(n) errors are significantly reduced for SCAN + PCM(ε = 4). For n ≥ 3, the errors are comparable to (and in some cases smaller than) the corresponding HF-MBE(n) errors.