Comparison between C IV- and Mg II-based black hole masses for our sample of z ∼ 5 − 5.7 quasars (teal diamonds) and for the E-XQR30 sample at z ≳ 6 (golden data points) from Mazzucchelli et al. (2023). The reported errorbars account only for the statistical contribution, while the systematic uncertainty due to the scaling relations (∼0.5 dex) is reported in the right-bottom corner, and is the same for the two samples.