The bolometric light curves of SN 2018ibb and historical slow-evolving SLSNe in the context of PISN models with nickel masses between 5 and 44 M_⊙. SN 2018ibb is the only SLSN whose entire light curve from t_max–93 to t_max+706 days is consistent with PISN templates. The other SLSNe have either too fast declining light curves, light curve shapes inconsistent with PISN models, or their light curves are poorly sampled, hindering a comparison with PISN templates. The grey-shaded region indicates the 1σ uncertainty.