Comparison of SN 2010ae and our N5def-hybrid models with 0%, 0.01%, 0.22%, and 36% helium abundances. Optical and infrared spectra have been normalised to the median flux from 5000 Å –7000 Å and 10 000 Å –12 000 Å, respectively. The optical and infrared spectra of SN 2010ae are approximately +16 days after B-band. The level of extinction experienced by SN 2010ae is highly uncertain (Stritzinger et al. 2014). Spectra presented here have been corrected for a total extinction of A_V = 1.9. Note that the infrared spectrum of SN 2010ae has been binned to Δλ = 5 Å. Our N5def-hybrid model is shown at +15 days after bolometric maximum light. Panels a and b: shaded regions represent He I λ5876, λ6678, λ7065, λ10830, and λ20587 at rest and blue-shifted by the maximum velocity of the model (∼6000 km s⁻¹). Panels c–g: zoom-ins of the regions surrounding He I λ5876, λ6678, λ7065, λ10830, and λ20587, respectively. Rest wavelengths are denoted by a vertical dashed line.