one further mannose ring from Man 8 GlcNAc 2 to make Man 7 GlcNAc 2 . This was unexpected because no mannosidase activity was detected when Htm1p was fi rst characterized (although it homologous to mannosidase enzymes). Man 7 GlcNAc 2 is then recognized by a protein called Yos9p. This protein specifi cally binds to the exposed mannose residue left after Htm1p’s trimming. Yos9p was already thought to “proofread” glycans that signal protein misfolding and target them for degradation, but until now the specifi c signal sought by Yos9p wasn’t clear. The work therefore provides important insights into how this arbiter of protein quality control operates in the ER. Clerc, S., et al. 2009. J. Cell Biol. doi:10.1083/jcb.200809198.