Understanding how neutrinos and antineutrinos interact with nuclei in the few-GeV regime is essential for precision neutrino oscillation measurements. Nuclear effects can change which particles emerge from an interaction and their energies, leading to biases in reconstructed neutrino energies if these effects are not modelled correctly. I will present the first measurement of the nuclear dependence of inclusive antineutrino scattering by the high-statistics cross-section experiment MINERvA. The results reveal clear shortcomings in current neutrino interaction models, particularly for heavier nuclei, and provide important constraints on neutrino interaction models and the treatment of nuclear effects in future oscillation analyses.