Nuclear modification factor ($R_{\text{pA}}$) of isolated prompt photon production in p--Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ and 8.16 TeV shown together with a measurement by the ATLAS collaboration in p--Pb collisions at $\sqrt{s_{\rm NN}}=8.16$ TeV. For illustration purposes, the data points at $\sqrt{s_{\text{NN}}}=5.02$ TeV are displaced by $\Delta p_{\rm T}=300$ MeV/$c$. The normalisation uncertainties are denoted as coloured boxes around unity.