Rest-frame UV spectrum of PSO167–13 obtained with our 2020 Magellan/FIRE observations (solid blue line), compared with the Venemans et al. (2015) spectrum (taken in 2014; solid red line). We have applied a median filter with a ≈ 20 Å kernel for visual purposes, as in Mazzucchelli et al. (2017). The average low-redshift QSO spectrum of Vanden Berk et al. (2001), normalized to the rest-frame 3000 Å flux of the Venemans et al. (2015) spectrum, is shown as a gray line. We also present the best fitting UV power law continuum of the 2020 spectrum as a dashed blue line, and the expected location of QSO emission lines at z = 6.515 as vertical dotted lines. We also show an example of atmospheric transmission during our FIRE observations (black line). Regions with transmission < 0.6 are marked with gray stripes. In particular, two spectral windows centered at rest frames ≈ 1800 Å and ≈ 2500 Å are completely affected by the very low atmospheric transmission and are thus masked in the spectra.