The paper ‘On the binary nature of the γ-ray sources AGL J2241+4454 (=MWC 656) and HESS J0632+057 (=MWC 148)’ was published in Mon. Not. R. Astron. Soc. 421, 1103–1112 (2012). We have recently discovered a small typo in the value of the zero phase used to produce the right-hand panel of Fig. 4. As a result, the orbital phase plotted is offset by approximately 0.5 with respect to the correct phase. The error affects only the phasing of the Hα emission-line parameters of MWC 148. The remainder of the paper, including Table 3 and Figs 6 and 7, is not affected. In this Erratum we provide a corrected version of Fig. 4. Note that now, with the correct phasing, the maximum in the equivalent width (EW) of the Hα line occurs ∼0.5 orbital phases past periastron.
We thank Diego F. Torres, Nanda Rea and Alessandro Papitto for pointing out the presence of a phase error in the published version of the right-hand panel in Fig. 4.