N‐Glycosylated substrates that undergo ER‐associated degradation (ERAD) are often deglycosylated by the cytosolic peptide:N‐glycanase (Ngly1) during their proteasomal degradation in the cytosol. Consequently, the presence of non‐ or deglycosylated forms of such proteins after treatment with proteasome inhibitors is widely used as evidence for cytosolic deglycosylation by Ngly1. However, in this study, the accumulation of nonglycosylated RTA∆m, a model ERAD substrate, was still observed in mouse cells lacking cytosolic de‐N‐glycosylating enzymes, when treated with proteasome inhibitors. It was found that RTA∆m is normally partially N‐glycosylated, while the nonglycosylated form is rapidly degraded by proteasomes in the cytosol. Our results suggest that the occurrence of ‘nonglycosylated’ ERAD substrates upon treatment with proteasome inhibitors is not necessarily a clue for cytosolic deglycosylation.