Average UV spectrum of our z ≃ 3 quasars as obtained from the stack of 37 SDSS observations (blue solid line; J0900+42 has been excluded). The spectrum was corrected for Galactic reddening and normalized to unity at 1450 Å (see Sect. 2). For comparison, we also plot the SDSS AGN composite of Vanden Berk et al. (2001, red solid line) and the stacked spectrum of z ∼ 2.4 quasars of Lusso et al. (2015, green solid line), corrected for IGM absorption shortwards of Lyα.